Chemistry Terms

Absorbance: The log of the reciprocal of the transmittance of light through a sample.

Absorption isotherm: A graph showing the relationship between the amount of adsorbate on a surface and its concentration in the surrounding medium.

Absorption spectra: The spectra produced when a substance absorbs light of specific wavelengths.

Absorption spectroscopy: A technique used to analyze the absorption of light by a substance.

Absorption spectrum: A spectrum showing the absorption of light by a substance as a function of wavelength or frequency.

Absorption: The uptake of a substance by another substance.

Accuracy: The closeness of a measured value to the true value.

Acetyl group: A functional group derived from acetic acid.

Acetylation: The addition of an acetyl group to a molecule.

Acetylene: A hydrocarbon with a triple bond between carbon atoms.

Acid anhydride: A compound formed when two carboxylic acid molecules lose water to form an ester.

Acid base pair: A conjugate acid-base pair that differs by a single proton.

Acid deposition: The deposition of acid-forming pollutants onto Earth’s surface.

Acid dissociation constant: A measure of the strength of an acid in solution.

Acid rain: Rainwater that is acidic due to dissolved pollutants.

Acid strength: A measure of the ability of an acid to donate protons.

Acid: A substance that donates protons in a chemical reaction.

Acid-base indicator: A substance that changes color in response to changes in pH.

Acid-base reaction: A chemical reaction involving the transfer of protons from an acid to a base.

Acid-base titration: A technique used to determine the concentration of an acid or base in a solution.

Acid-catalyzed reaction: A reaction that is catalyzed by an acid.

Acidic solution: A solution with a pH less than 7.

Acidity: The measure of the concentration of protons in a solution.

Activation energy: The minimum amount of energy required for a chemical reaction to occur.

Active site: The region of an enzyme where substrate molecules bind and undergo a chemical reaction.

Activity series: A list of metals in order of their reactivity with acids.

Acyl group: A functional group derived from a carboxylic acid by removing the hydroxyl group.

Adsorbate: The substance that is adsorbed onto a surface in adsorption.

Adsorbent: A material that adsorbs other substances onto its surface.

Adsorption isotherm: A graph showing the relationship between the amount of adsorbate on a surface and its concentration in the surrounding medium.

Adsorption: The adherence of molecules to a surface.

Aerobic: Requiring oxygen to survive or grow.

Aerosol: A suspension of fine particles or liquid droplets in air.

Alcohol: An organic compound containing a hydroxyl group bonded to a saturated carbon atom.

Aldehyde: An organic compound containing a carbonyl group bonded to a hydrogen atom.

Alkali metal: An element in Group 1 of the periodic table.

Alkali: A base that dissolves in water to form hydroxide ions.

Alkaline earth metal: An element in Group 2 of the periodic table.

Alkaloid: A nitrogen-containing compound found in plants.

Alkane: A hydrocarbon with single bonds between carbon atoms.

Alkene: A hydrocarbon with at least one double bond between carbon atoms.

Alkoxide: A compound derived from an alcohol by removing a hydrogen atom.

Alkyl group: An organic group derived from an alkane by removing one hydrogen atom.

Alkyl halide: An organic compound containing a halogen atom bonded to an alkyl group.

Allotropy: The existence of an element in multiple forms with different structures.

Alloy: A mixture of two or more metals.

Alloying: The process of mixing two or more metals to form an alloy.

Alpha decay: The radioactive decay of a nucleus by emitting an alpha particle.

Alpha helix: A type of secondary structure in proteins where the polypeptide chain coils into a helix.

Alpha particle: A type of radiation emitted by some radioactive isotopes.

Alpha particle: A type of radiation emitted by some radioactive isotopes.

Aluminum: A metallic element with the symbol Al and atomic number 13.

Amide: An organic compound containing a carbonyl group bonded to a nitrogen atom.

Amine: An organic compound containing a nitrogen atom bonded to hydrogen or carbon atoms.

Amorphous solid: A solid without a regular crystalline structure.

Amorphous: A solid without a regular crystalline structure.

Ampere: The unit of electric current.

Amphoteric: A substance that can act as both an acid and a base.

Amplitude: The maximum displacement of a wave from its equilibrium position.

Analyte: The substance being analyzed in a chemical analysis.

Analytical chemistry: The branch of chemistry that studies the composition of materials.

Anhydrous: A substance without water molecules.

Anion: A negatively charged ion.

Anode: The electrode in an electrolytic cell where oxidation occurs.

Antibonding orbital: An orbital that destabilizes a molecule and weakens its bond.

Antimony: A metalloid element with the symbol Sb and atomic number 51.

Antioxidant: A substance that inhibits oxidation reactions.

Aqueous solution: A solution in which water is the solvent.

Aqueous: A solution in which water is the solvent.

Archimedes’ principle: The buoyant force on an object is equal to the weight of the fluid it displaces.

Arene: A compound containing a ring of carbon atoms with alternating single and double bonds.

Aromatic compound: A compound containing an aromatic ring, such as benzene.

Aromatic: A compound containing a ring of delocalized electrons.

Arrhenius acid: A substance that donates protons in water.

Arrhenius equation: A mathematical equation that describes the rate of a chemical reaction.

Asymmetry: Lack of symmetry in a molecular structure.

Atmospheric pressure: The pressure exerted by the atmosphere on Earth’s surface.

Atom economy: A measure of the efficiency of a chemical reaction in producing useful products.

Atom: The smallest unit of an element that retains its chemical properties.

Atomic absorption spectroscopy: A technique used to analyze the absorption of light by atoms.

Atomic emission spectroscopy: A technique used to analyze the emission of light by atoms.

Atomic mass unit (amu): A unit of mass used to express the mass of atoms and molecules.

Atomic mass: The mass of an atom expressed in atomic mass units.

Atomic number: The number of protons in the nucleus of an atom.

Atomic orbital: A region of space where an electron is likely to be found within an atom.

Atomic radius: The size of an atom, typically measured as the distance from the nucleus to the outermost electrons.

Atomic theory: The theory that all matter is composed of atoms.

Atomic weight: The average weight of an atom of an element, taking into account its isotopes.

Atomization: The process of converting a sample into individual gas-phase atoms.

Autoclave: A device used to sterilize equipment using high pressure and heat.

Autoionization: The process by which two molecules of a substance react to form ions.

Autoradiography: A technique used to detect the presence of radioactive isotopes.

Average atomic mass: The weighted average of the masses of the isotopes of an element.

Avogadro’s hypothesis: Equal volumes of gases at the same temperature and pressure contain the same number of particles.

Avogadro’s hypothesis: Equal volumes of gases at the same temperature and pressure contain the same number of particles.

Avogadro’s law: Equal volumes of gases at the same temperature and pressure contain the same number of particles.

Avogadro’s number: The number of atoms, molecules, or particles in one mole of a substance.

Avogadro’s number: The number of atoms, molecules, or particles in one mole of a substance.

Azo compound: A compound containing a nitrogen-nitrogen double bond.

B oxidation: A metabolic process that breaks down fatty acids into acetyl-CoA.

Background radiation: The constant low-level radiation present in the environment.

Back-titration: A technique used to determine the amount of a substance by reacting it with an excess of another reagent.

Bacterial cellulose: Cellulose produced by bacteria and used in various applications.

Bacterial growth curve: The growth phases observed in bacterial cultures – lag, log, stationary, and death phases.

Bacterial transformation: The alteration of bacterial cells through the uptake of foreign DNA.

Balancing chemical equations: Ensuring the number of atoms is the same on both sides.

Baldridge–Klopman chemistry function: A quantum mechanical approach to establishing molecular orbital relationships.

Band theory of solids: A model explaining the electrical properties of solids based on energy bands.

Barfoed’s test: A chemical test used to distinguish between monosaccharides and disaccharides.

Barium carbonate: A chemical compound used in various applications, including the manufacture of ceramics.

Barium hydroxide: A chemical compound with the formula Ba(OH)2.

Barium nitrate: A white crystalline compound used in fireworks and explosives.

Barium sulfate: A white insoluble compound used in medical imaging as a contrast agent.

Barometer: A device used to measure atmospheric pressure.

Base: A substance that accepts protons in a chemical reaction.

Basic anhydride: A metal oxide that reacts with water to form a base.

Basic oxides: Metal oxides that react with acids to form salts and water.

Bass for identification of substances: A technique for identifying substances via their behavior with reagents.

Batch crystallization: A method of crystallizing materials in isolated batches.

Batch distillation: A distillation process carried out in batches rather than continuous flow.

Batch reactor: A type of chemical reactor where reactants are added and products removed at intervals.

Bauxite: A mineral ore rich in aluminum oxide used as the primary source of aluminum.

Bayliss theory: The theory of how oxygen levels in the blood regulate breathing.

Beamline: A specialized area along a synchrotron used for experiments in various scientific fields.

Beckmann rearrangement: A rearrangement reaction used to convert oximes to amides.

Bedach chromatography: A type of column chromatography used to separate proteins.

Beers law: A relationship between the absorption of light and the concentration of a solute in a solution.

Bell–Evans–Polanyi principle: A principle describing the relationship between activation energy and reaction rate.

Benzene: A cyclic hydrocarbon with alternating double bonds.

Benzofuran: A heterocyclic compound containing a benzene and furan ring.

Benzophenone: An aromatic ketone used in the synthesis of organic compounds.

Benzoyl peroxide: An organic compound used in acne treatments.

Benzyl alcohol: An aromatic alcohol with the formula C6H5CH2OH.

Berry pseudorotation: A type of molecular motion observed in some five-coordinate compounds.

Beryllium: A light metal element with the symbol Be and atomic number 4.

Bile salt: A component of bile involved in fat digestion and absorption.

Bimolecular collision: The collision of two molecules leading to a chemical reaction.

Bimolecular reaction: A chemical reaction involving the collision of two molecules.

Binary addition: The process of adding binary numbers in digital systems.

Binary alloy: A solid solution of two metallic elements.

Binary compound: A compound composed of two elements.

Binary fission: A type of asexual reproduction in single-celled organisms.

Binary mixture: A mixture composed of two different substances.

Binary nucleation: The simultaneous nucleation of two different phases in a given system.

Binary vapor cycle: A thermodynamic cycle involving two-phase vapor-liquid mixtures.

Binding energy: The energy required to separate a nucleus into its individual nucleons.

Binding site: The specific region on a molecule where another molecule can bind.

Binomial distribution: A probability distribution describing the outcome of a binary event.

Bioactive compound: A compound that has a biological effect when consumed or applied.

Biochemistry: The study of chemical processes in living organisms.

Biodegradation: The breakdown of organic substances by microorganisms.

Biological half-life: The time it takes for a substance to be reduced by half in a living organism.

Biological oxygen demand (BOD): The amount of oxygen needed by microorganisms to break down organic materials in water.

Biosensor: An analytical device that combines a biological component with a physicochemical detector.

Biotin: Also known as Vitamin B7, it is a water-soluble vitamin important for metabolism.

Biotite: A common phyllosilicate mineral rich in potassium and magnesium.

Biotransformation: The process by which a substance is chemically altered within an organism.

Birkeland–Eyde process: A method for the industrial production of nitrogen oxides.

Bismuth: A metal element with the symbol Bi and atomic number 83.

Bisphenol A: An organic compound used in the production of plastics.

Bisulfate ion: The polyatomic ion HSO4-.

Bitumen: A viscous mixture of hydrocarbons derived from crude oil.

Biuret test: A chemical test used to detect the presence of proteins based on peptide bonds.

Blast furnace: A furnace used for smelting ores to produce metals like iron.

Bohr magneton: A unit of magnetic moment used in quantum mechanics.

Boiling liquid expanding vapor explosion (BLEVE): An explosion caused by the rupture of a vessel containing a pressurized liquid.

Boiling point elevation: The increase in the boiling point of a solvent in the presence of a solute.

Boiling point: The temperature at which a substance changes from liquid to gas.

Boiling stone: Also known as boiling chips, used to promote even boiling in a liquid.

Bond cleavage: The breaking of a covalent bond in a chemical reaction.

Bond dipole moment: The measure of the separation of positive and negative charges in a chemical bond.

Bond energy: The energy required to break a chemical bond.

Borate: A salt or ester of boric acid containing the BO3 group.

Boron: A metalloid element with the symbol B and atomic number 5.

Borosilicate glass: A type of glass containing boron trioxide and silica, known for its resistance to thermal shock.

Bose–Einstein statistics: A quantum statistics for particles with integer spin.

Bottom-up synthesis: A method of nanomaterial synthesis starting from individual atoms or molecules.

Bovine serum albumin (BSA): A protein derived from cows’ blood commonly used in research and diagnostics.

Brackish water: Water that is saltier than freshwater but not as salty as seawater.

Branched chain: A hydrocarbon chain with one or more side chains or branches.

Bravais lattice: A mathematical description of the periodic arrangement of atoms in a crystal lattice.

Brinkmann tube: A specialized tube used in the laboratory for gas purification.

Bristol volume: A measure of the capacity of a container.

Bromination: The addition of a bromine atom to a compound or molecule.

Bromine: A halogen element with the symbol Br and atomic number 35.

Bromocresol purple: An acid-base indicator that changes color in the pH range of 5.2 to 6.8.

Bromothymol blue: A pH indicator that changes color between acidic and basic pH ranges.

Buchner funnel: A piece of laboratory equipment used for vacuum filtration.

Buckyball: A fullerene molecule with a spherical shape, composed of carbon atoms.

Buffer solution: A solution that resists changes in pH when an acid or base is added.

Buffer: A solution that resists changes in pH.

Buffering agent: A substance added to a solution to maintain its pH.

Buffering capacity: The ability of a buffer solution to resist pH changes.

Bunge method: A method used to determine the viscosity of molten plastics.

Bunsen burner: A gas flame used in laboratories for heating.

Bunsen cell: A type of electric cell used for temporary electrical experiments.

Bunsen cell: An early electric cell used in scientific experiments.

Burner: A device used to produce a flame for heating purposes in laboratories.

Butane: A hydrocarbon with four carbon atoms in a straight chain.

Calcium: An alkaline earth metal with the symbol Ca and atomic number 20.

Calorie: A unit of energy defined as the amount of heat needed to raise one gram of water by one degree Celsius.

Calorimeter: A device used to measure heat changes in chemical reactions.

Calorimetry: The measurement of heat changes in a chemical reaction.

Capillary action: The movement of liquid in narrow spaces due to surface tension.

Capillary column: A narrow column used in gas chromatography for separating compounds.

Capillary electrophoresis: A technique for separating ions based on their charge and size.

Carbanion: A negatively charged carbon atom.

Carbocation rearrangement: The migration of a carbocation to form a more stable intermediate.

Carbocation: A positively charged carbon atom.

Carbocation: A positively charged carbon ion.

Carbohydrate: A biomolecule composed of carbon, hydrogen, and oxygen.

Carbonate: A salt or ester of carbonic acid.

Carbonyl compound: A compound containing a carbonyl group.

Carbonyl group: A functional group containing a carbon atom double-bonded to an oxygen atom.

Carboxylate ion: The ion formed by deprotonation of a carboxylic acid.

Carboxylation: The addition of a carboxyl group to a molecule.

Carboxylic acid: An organic compound containing a carboxyl functional group.

Carnot cycle: An idealized thermodynamic cycle involving reversible processes.

Carotenoid: Pigments found in plants responsible for their colors.

Cascade reaction: A series of sequential reactions where the product of one becomes the reactant of the next.

Catabolism: The breakdown of complex molecules into simpler ones.

Catalysis: The process of increasing the rate of a chemical reaction.

Catalyst poisoning: The deactivation of a catalyst by a foreign substance.

Catalyst: A substance that increases the rate of a chemical reaction without being consumed.

Catalytic converter: A device that converts harmful emissions into less harmful substances.

Cathode: The electrode where reduction occurs in an electrochemical cell.

Cation exchange: The process of exchanging cations in a solution.

Cation: A positively charged ion.

Cavity ring-down spectroscopy: A sensitive analytical technique for measuring trace gas concentrations.

Cellulose: A polysaccharide found in plant cell walls.

Centrifugation: A technique that separates components of a mixture based on density differences.

Chain reaction: A series of reactions in which each step generates a new reactive species.

Chelating agent: A compound that forms multiple coordinate bonds with a metal ion.

Chelation therapy: A medical treatment to remove heavy metals from the body.

Chelation: The formation of multiple coordinate bonds between a metal ion and ligands.

Chemical bond: The force holding atoms together in a molecule.

Chemical equation: A symbolic representation of a chemical reaction.

Chemical equilibrium: A state in which the rate of the forward and reverse reactions are equal.

Chemical kinetics: The study of reaction rates and mechanisms.

Chiral center: An atom in a molecule that has four different substituents.

Chiral: A molecule that is not superimposable on its mirror image.

Chlorine: A halogen element with the symbol Cl and atomic number 17.

Chloroform: A volatile solvent with the formula CHCl3.

Chromate: A compound containing the chromate ion (CrO4^2-).

Chromatography: A technique used to separate components in a mixture.

Chromophore: The part of a molecule responsible for its color.

Chromophore: The part of a molecule responsible for its color.

Cisplatin: A chemotherapy drug used to treat cancer.

Cis-trans isomerism: Isomerism due to the different arrangement of groups around a double bond.

Claisen condensation: A reaction between two esters to form a beta-keto ester.

Cloud point: The temperature at which a solute precipitates from a solution.

Coacervation: The separation of a liquid phase from a solution.

Coefficient: The number that appears before a compound in a chemical equation.

Coenzyme: An organic molecule that assists enzymes in their function.

Coenzyme: An organic molecule that helps enzymes carry out biochemical reactions.

Collagen: A structural protein found in connective tissues.

Colligative properties: Properties of solutions that depend on the number of solute particles.

Colligative property: A property of solutions dependent on the concentration of solute particles.

Collision theory: The theory that chemical reactions occur when reactant molecules collide with sufficient energy.

Column chromatography: A separation technique based on the differential adsorption of components.

Combinatorial chemistry: The rapid synthesis and screening of large numbers of compounds.

Combustion: A chemical reaction involving the rapid oxidation of a fuel.

Complementary base pairing: The specific hydrogen bonding of nitrogenous bases in DNA and RNA.

Compound: A substance made up of two or more elements.

Concentrated: A solution with a high amount of solute compared to the solvent.

Concentration: The amount of solute present in a given amount of solvent.

Condensation polymerization: A process where monomers join together, releasing a small molecule.

Condensation: The process of a gas turning into a liquid.

Conductance: The measure of an electrical conductor’s ability to conduct electricity.

Conductivity: The ability of a substance to conduct electricity.

Conformational isomerism: Different spatial arrangements of atoms in a molecule due to rotations around single bonds.

Conjugate acid: The species formed when a base accepts a proton.

Conjugate acid-base pair: Two species related by the gain or loss of a proton in a chemical reaction.

Conjugated system: A system of alternating double and single bonds.

Contact process: A method for producing sulfuric acid from sulfur dioxide.

Coordinate covalent bond: A covalent bond where both shared electrons come from one atom.

Coordination complex: A molecule containing a central metal ion and surrounding ligands.

Coordination number: The number of ligands surrounding a central metal ion in a complex.

Copolymer: A polymer made from two or more different monomers.

Corrosion: The deterioration of a material through chemical reactions.

Countercurrent exchange: The flow of substances in opposite directions to maximize exchange.

Coupling reaction: A reaction that joins two smaller molecules to form a larger one.

Covalent bond: A chemical bond formed by the sharing of electron pairs between atoms.

Critical mass: The minimum amount of fissile material required for a nuclear chain reaction.

Critical point: The temperature and pressure at which a substance’s liquid and gas phases are indistinguishable.

Critical temperature: The temperature above which a gas cannot be liquefied.

Cross-linking: The formation of covalent bonds between polymer chains.

Cryogenics: The study of extremely low temperatures.

Crystalline: A solid with a regular repeating atomic arrangement.

Crystallization: The process of forming crystals from a liquid or solution.

Curie law: A relationship between magnetic susceptibility and temperature.

Curie temperature: The temperature at which a material loses its magnetic properties.

Curie: A unit of radioactivity equal to the activity of one gram of radium.

Cyanide: A highly toxic compound containing the CN- ion.

Cyclization: The process of forming a ring structure in a molecule.

Cycloaddition: A reaction where two or more unsaturated molecules form a ring.

Cycloalkane: A cyclic hydrocarbon with single bonds between carbon atoms.

Cyclohexane: A cyclic hydrocarbon with six carbon atoms.

Cyclohexanone: A cyclic ketone compound.

Darzen reaction: A reaction between a ketone and a sulfonic acid to form an α,β-unsaturated ketone.

Debye length: A measure of the distance over which charges in a solution can influence each other.

Decantation: A separation technique where a liquid is poured off, leaving solid particles behind.

Decarboxylation: The removal of a carboxyl group from a molecule, often releasing carbon dioxide.

Decomposition: The breakdown of a compound into simpler substances through a chemical reaction.

Degree of unsaturation: A value representing the number of rings and multiple bonds in a molecule.

Dehydration: The removal of water molecules from a substance or compound.

Deliquescence: The process of a solid absorbing moisture from the air and dissolving in it.

Delocalization: The spread of electron density over multiple atoms in a molecule or ion.

Denaturation: The process of altering the structure of a protein, causing it to lose its biological activity.

Density: The mass of a substance per unit volume.

Denuder: A device used to remove specific gases or particles from a gas stream.

Deoxyribonucleic acid (DNA): A molecule that carries genetic information in most living organisms.

Deprotonation: The loss of a proton from a molecule, forming its conjugate base.

Dialdehyde: A compound containing two aldehyde functional groups.

Dialkyl: A term referring to a group containing two alkyl (carbon-based) groups.

Dialysis bag: A semipermeable membrane bag used in laboratory settings to mimic cell membranes.

Dialysis tubing: A selectively permeable membrane used in laboratory experiments for dialysis.

Dialysis: The process of separating solutes in a solution based on their different diffusion rates through a semipermeable membrane.

Diamagnetic: A material that is not attracted to magnetic fields.

Diastereomer: Stereoisomers that are not mirror images of each other and have different physical properties.

Diatomic molecule: A molecule composed of two atoms of the same or different elements.

Diazonium salt: A compound containing a nitrogen-nitrogen double bond and a positive charge.

Diels-Alder reaction: A cycloaddition reaction between a conjugated diene and dienophile.

Diester: An organic compound containing two ester functional groups.

Diethyl ether: A volatile solvent with the formula (C2H5)2O, commonly known as ether.

Diethylamine: A secondary amine with the formula (C2H5)2NH.

Diffusion coefficient: A measure of the speed at which a substance diffuses in a medium.

Diffusion: The movement of molecules from an area of high concentration to an area of low concentration.

Dimethyl sulfoxide (DMSO): A widely used solvent with applications in biochemistry and organic synthesis.

Dioxygen difluoride: A highly reactive compound consisting of oxygen and fluorine.

Dipole moment: A measure of the separation of positive and negative charges in a molecule.

Dipole-dipole interaction: A type of intermolecular force between molecules with permanent dipoles.

Diprotic acid: An acid that can donate two protons in successive dissociation steps.

Direct analysis in real time (DART): A technique for rapid mass spectrometry analysis of samples in open air.

Disaccharide: A carbohydrate molecule composed of two monosaccharide units joined by a glycosidic bond.

Discrete: Referring to a distinct and separate entity in the context of chemistry.

Disinfectant: A chemical agent that kills or inhibits the growth of microorganisms on surfaces.

Displacement reaction: A chemical reaction in which more reactive element displaces a less reactive element in a compound.

Disproportionation: A redox reaction in which the same element is simultaneously oxidized and reduced.

Dissociation: The process by which a compound breaks down into its constituent ions or molecules.

Dissolution: The process of a solute mixing with a solvent to form a solution.

Distal: A term used in biochemistry to describe the part of a molecule farthest from a specified reference point.

Distillation: A process that involves separating components of a mixture based on differences in their volatilities.

Disulfide bond: A covalent bond between two sulfur atoms, important in protein structure.

Dopant: An impurity intentionally added to a semiconductor to modify its electrical properties.

Doping: The intentional addition of impurities to a semiconductor to alter its electrical properties.

Double bond: A covalent bond in which two pairs of electrons are shared between two atoms.

Double displacement reaction: A chemical reaction in which cations and anions of two compounds switch places.

Ductility: The ability of a material to deform without breaking under tensile stress.

Effective nuclear charge: The net positive charge acting on an electron in an atom.

Effective nuclear charge: The net positive charge experienced by an electron in an atom.

Eggert-Krause method: A technique used to determine the oxygen content of organic compounds.

Eigenvalue: The value that represents an observable property in quantum mechanics.

Einthoven triangle: An imaginary equilateral triangle representing the standard bipolar limb leads in electrocardiography.

Electrochemical cell: A system that converts chemical energy into electrical energy.

Electrochemical cell: A system that converts chemical energy into electrical energy.

Electrochemical potential: The potential difference between a half-reaction and a standard hydrogen electrode.

Electrodynamics: The study of the interaction between electric charges and currents.

Electrolysis: The process of using electrical energy to drive a non-spontaneous chemical reaction.

Electrolyte: A substance that conducts electricity when dissolved in water.

Electrolytic cell: A cell that uses electrical energy to drive non-spontaneous chemical reactions.

Electrolytic solution: A solution that conducts electricity through the movement of ions.

Electron affinity: The energy change when an atom gains an electron.

Electron affinity: The energy released when an atom gains an electron to form an anion.

Electron capture: The process in which an inner orbital electron is captured by a nucleus.

Electron cloud: The region around the nucleus where electrons are likely to be found.

Electron configuration: The arrangement of electrons in an atom’s energy levels.

Electron configuration: The arrangement of electrons in the energy levels of an atom.

Electron density: A measure of the probability of finding an electron in a specific region.

Electron donor: A substance that donates electrons in a chemical reaction.

Electron paramagnetic resonance: A technique used to study the interactions of unpaired electrons with magnetic fields.

Electron transfer: The movement of electrons from one species to another.

Electron transport chain: A series of protein complexes in cellular respiration that generate ATP.

Electron transport chain: A series of protein complexes in mitochondria that produces ATP.

Electron: A subatomic particle with a negative charge found in atoms.

Electronegativity: The ability of an atom to attract electrons in a chemical bond.

Electronegativity: The tendency of an atom to attract shared electrons in a chemical bond.

Electroosmosis: The movement of a solvent under the influence of an electric field.

Electrophile: A species that is electron deficient and seeks electrons.

Electrophilic addition: A reaction where an electrophile attaches to an unsaturated compound.

Electrophilic aromatic substitution: A type of organic reaction on an aromatic compound.

Electrophilic aromatic substitution: A type of reaction where an electrophile replaces another atom or group on an aromatic ring.

Electrophoresis: A method used to separate charged molecules based on size and charge.

Electrophoresis: A technique used to separate molecules based on their charge and size.

Electrostatic attraction: The force between oppositely charged particles.

Element: A pure substance made up of only one type of atom.

Elemental analysis: The determination of the elemental composition of a sample.

Emission line: A line in an emission spectrum representing a specific wavelength of light.

Emission spectrum: The range of wavelengths of light emitted by an element.

Emission spectrum: The range of wavelengths of light emitted by an element when its electrons transition from excited states to ground states.

Emission spectrum: The series of wavelengths emitted by an excited atom or molecule.

Emission spectrum: The spectrum of light emitted by an element when excited.

Empirical formula: The simplest ratio of elements in a compound.

Emulsifier: A substance that stabilizes emulsions and prevents separation of immiscible liquids.

Emulsion: A mixture of two immiscible liquids stabilized by an emulsifier.

Enantiomer: Stereoisomers that are mirror images of each other and non-superimposable.

End group: The atoms or groups at the ends of a polymer chain.

End-group analysis: A method used to determine the chemical groups present at the ends of a polymer chain.

Endothermic reaction: A reaction that absorbs heat from the surroundings.

Endothermic reaction: A reaction that absorbs heat from the surroundings.

Endothermic: A reaction that absorbs heat from the surroundings.

Energy diagram: A graph that shows the energy changes in a chemical reaction.

Energy level: The specific energies electrons can have in an atom.

Energy: The capacity of a system to do work or produce heat.

Enol tautomerism: The interconversion between keto and enol forms of a compound.

Enol: A functional group containing a double bond between a carbon and an alcohol group.

Enthalpy change: The heat energy exchanged in a chemical reaction.

Enthalpy of formation: The heat change when a compound is formed from its elements.

Enthalpy: The heat content of a system at constant pressure.

Entropy change: The measure of disorder or randomness in a system during a process.

Entropy: A measure of disorder or randomness in a system.

Enzyme inhibition: The process by which enzymes are inhibited from catalyzing a reaction.

Enzyme kinetics: The study of the rates of enzyme-catalyzed reactions.

Enzyme specificity: The selectivity of an enzyme toward its substrate.

Enzyme substrate: The molecule upon which an enzyme acts.

Enzyme: A biological catalyst that speeds up chemical reactions in living organisms.

Enzyme-substrate complex: The temporary intermediate formed during enzyme-catalyzed reactions.

Epoxide: A cyclic ether with a three-membered ring containing an oxygen atom.

Equatorial bond: A bond that lies in the same plane as the ring in a cyclohexane structure.

Equatorial position: The position of a substituent in a molecule in the plane of the ring.

Equatorial: The position of an atom in a molecule in the plane of the ring.

Equilibrium constant: A numerical value that indicates the position of a chemical equilibrium.

Equilibrium constant: The ratio of products to reactants at equilibrium.

Equilibrium shift: The change in equilibrium position in response to a disturbance.

Equilibrium: A state in a chemical reaction where the concentrations of reactants and products remain constant.

Equivalence point: The point in a titration where the acid and base are stoichiometrically equivalent.

Equivalence point: The point in a titration where the moles of acids equal the moles of base.

Erasable programmable read-only memory (EPROM): A type of memory chip that can be erased and reprogrammed.

Ester: A compound formed by the reaction of an alcohol and a carboxylic acid.

Esterification: The chemical reaction in which an alcohol and a carboxylic acid form an ester and water.

Ether: An organic compound containing an oxygen atom bonded to two alkyl or aryl groups.

Eutectic mixture: A mixture of substances that has the lowest melting point possible.

Eutectic point: The temperature at which a eutectic mixture undergoes complete solidification or melting.

Eutectic point: The temperature at which a mixture of substances has the lowest melting point.

Eutrophication: The overabundance of nutrients in a body of water leading to algal blooms.

Evaporate: The process of converting a liquid to a gas by heating.

Evaporation: The process of a liquid turning into a gas at temperatures below its boiling point.

Evaporative cooling: The process of cooling by the evaporation of a liquid.

Excimer: A dimer in an excited state that is formed by the association of two excited-state molecules.

Exciplex: An excited-state complex formed between two different species.

Excitation: The process of moving an electron to a higher energy level.

Excited state: A higher energy state of an atom or molecule than the ground state.

Excited state: A state in which an atom or molecule has absorbed energy.

Excited state: A state in which an atom or molecule has absorbed energy.

Exciton: A bound state of an electron and hole in a semiconductor.

Exclusion limit: The molecular weight above which particles are excluded from entering a gel filtration column.

Exergonic: A reaction where the products have lower energy than the reactants.

Exothermic reaction: A reaction that releases heat to the surroundings.

Exothermic: A reaction that releases heat to the surroundings.

Fahrenheit: A temperature scale where water freezes at 32 degrees and boils at 212 degrees.

Fajans’ rules: Rules used to predict the ionic character of chemical bonds.

Faraday’s laws of electrolysis: Laws explaining the relationship between the amount of material produced during electrolysis and the amount of electricity passed through the cell.

Fatty acid: A carboxylic acid with a long aliphatic tail, found in fats and oils.

Fatty alcohols: Long-chain alcohols derived from natural fats and oils.

F-block: The group of elements in the periodic table with partially filled f-orbitals.

Fehling’s solution: A chemical reagent used to test for the presence of reducing sugars in a solution.

Fermentation broth: The liquid mixture containing microorganisms and nutrients used in fermentation.

Fermentation: A metabolic process in which sugars are converted into alcohol and gases by microbes.

Fermentation: The process of converting sugars into alcohol using microorganisms.

Ferric oxide: A compound of iron and oxygen with the chemical formula Fe2O3.

Ferric: Relating to iron with a +3 oxidation state.

Ferroelectric: Materials with a spontaneous electric polarization that can be reversed by an electric field.

Ferromagnetic: Materials that are strongly attracted to magnets and can retain magnetization.

Ferrous: Relating to iron with a +2 oxidation state.

Fick’s laws of diffusion: Mathematical models that describe the transport of substances through a concentration gradient.

Field emission: The penetration of an electric field causing the emission of electrons from a surface.

Field-emission microscopy: A microscopy technique that uses electric fields to enhance spatial resolution.

Filiform corrosion: A localized form of corrosion that spreads along a metal’s surface.

Filtering crucible: A heat-resistant container with a porous bottom used for filtration.

Filtrate: The liquid that passes through a filter during filtration.

Filtration: A method of separating solid particles from a liquid using a filter medium.

Fire point: The lowest temperature at which a substance’s vapor continues to burn after ignition.

Fischer esterification: A chemical reaction between a carboxylic acid and an alcohol to form an ester, catalyzed by an acid.

Fischer projection: A 2D representation that shows the spatial arrangement of atoms in a molecule, commonly used for carbohydrates.

Fischer-Tropsch process: A catalytic reaction that converts syngas (a mixture of carbon monoxide and hydrogen) into hydrocarbons.

Fission product: The isotopes produced by the fission of heavy atomic nuclei.

Fission: The splitting of a heavy atomic nucleus into lighter nuclei and release of energy.

Fixed bed reactor: A chemical reactor in which a solid catalyst is packed and reactants flow through the catalyst bed.

Fixed oil: A non-volatile oil that does not evaporate easily at room temperature.

Flame atomic absorption spectroscopy: A technique used to analyze the concentration of metals in a sample based on the absorption of light by the vaporized metal atoms in a flame.

Flame emission spectroscopy: A technique that analyzes the emission spectrum produced when elements in a sample are burned in a flame.

Flame ionization detector: A device used in gas chromatography to detect organic compounds based on ionization.

Flame photometry: A technique for quantitative analysis based on the color emitted by the elements in a flame.

Flame retardant: A substance added to materials to reduce their flammability and slow down the spread of fire.

Flame retardant: A substance that reduces the flammability of materials.

Flame test: A procedure for identifying elements by the color of flame they produce when burned.

Flammable: Easily ignited and capable of burning rapidly.

Flash chromatography: A fast form of column chromatography used to separate mixtures of compounds.

Flash evaporation: A rapid vaporization process that occurs when liquids undergo sudden depressurization.

Flash point: The lowest temperature at which a liquid gives off vapor to form an ignitable mixture.

Flexible: Capable of being bent or shaped without breaking.

Floc: A cluster of particles formed in a suspension or colloid.

Flocculant: A substance used to provoke the formation of flocs in an emulsion.

Flocculation: The process of forming clusters of particles in a suspension.

Flotation: A technique used to separate minerals from ores based on their hydrophobicity.

Flow reactor: A type of chemical reactor in which reactants continuously flow through the system.

Fluid mechanics: The study of fluids in motion and at rest, including liquids and gases.

Fluorapatite: A mineral containing calcium phosphate and fluoride, commonly found in teeth and bones.

Fluorescence microscopy: A technique that uses fluorescence to study the distribution of specific molecules within tissues or cells.

Fluorescence spectroscopy: A technique that measures the emitted light following excitation of a sample with light of a specific wavelength.

Fluorescence: The emission of light by a substance when exposed to ultraviolet or visible light.

Fluoridation: The process of adding fluoride to water to improve dental health.

Fluoride: An inorganic anion of fluorine commonly found in toothpaste and drinking water for dental health.

Fluorine: A highly reactive, pale yellow gas element with the symbol F.

Fluorochrome: A fluorescent dye used to stain biological specimens for microscopy.

Fluorometer: An instrument used to measure the amount of fluorescence emitted by a sample.

Fluorophore: A fluorescent chemical compound that emits light when exposed to specific wavelengths.

Fluorosis: A condition caused by excessive fluoride intake characterized by dental fluorosis and skeletal fluorosis.

Focal length: The distance between the center of a lens and the point where light rays converge.

Focal plane: The plane in which parallel light rays are brought to a focus by a lens.

Force field: A mathematical model that describes how forces affect objects in space.

Formal charge: A method used to assign charges to individual atoms in a molecule based on electron distribution.

Formaldehyde: A colorless, strong-smelling chemical used in building materials and household products.

Formalin: A formaldehyde solution used as a disinfectant or preservative.

Formalism: A specific mathematical framework to describe physical systems.

Formic acid: A colorless liquid with a pungent odor used in various industries.

Formula: A symbolic representation showing the number and type of atoms in a compound.

Fossil fuel: A natural fuel formed from the remains of living organisms.

Fraction: A part of a mixture with distinct properties.

Fractional crystallization: A method of separating components in a mixture based on their differing solubilities.

Fractional crystallization: A separation process that involves the gradual cooling of a solution to isolate different components based on their solubilities.

Fractional distillation: A method of separating a mixture of liquids with different boiling points.

Fractional precipitation: A method used to separate ions from a solution based on their differing solubilities at different pH levels.

Fractionation: The process of separating a mixture into individual components.

Franck-Condon principle: A rule stating that transitions between electronic states occur so quickly that nuclei remain stationary.

Free energy: A thermodynamic property that represents the maximum reversible work that can be extracted from a system.

Free expansion: A process where a gas expands into a vacuum without doing work on the surroundings.

Free radical: A highly reactive species with one or more unpaired electrons.

Freezing point depression: The phenomenon where adding a solute lowers the freezing point of a solvent.

Freezing point: The temperature at which a liquid changes into a solid.

Fretting corrosion: Wear and corrosion that occur at the contact interface between assembly parts undergoing small oscillatory motions.

Frictional force: A force that resists the relative motion of solid surfaces or fluid layers sliding against each other.

Frit: A porous glass disk used in chromatography to support the stationary phase.

Froth flotation: A method for separating hydrophobic minerals from ores by using air bubbles.

Fructose: A simple sugar found in fruits and honey, also known as fruit sugar.

Fuel cell: A device that converts the chemical energy of a fuel into electrical energy through an electrochemical reaction.

Fuel consumption: The amount of fuel used by an engine or system per unit of time.

Fugacity coefficient: A correction factor that accounts for the deviation from ideal gas behavior in real gases.

Fugacity: A measure of the escaping tendency of a substance from a mixture.

Fulminate: A class of explosive compounds containing metal ions and an organic radical.

Fumaric acid: A dicarboxylic acid that occurs naturally in various plants.

Fume event: A sudden release of smoke, fumes, or noxious gases often associated with industrial accidents.

Fume hood: A ventilated enclosure used in laboratories to safely handle toxic fumes.

Fume: A suspension of fine solid particles in a gas or vapor.

Functional group: A specific arrangement of atoms in a compound that gives it characteristic chemical properties.

Functional group: A specific group of atoms responsible for the characteristic chemical reactions of a molecule.

Funk: A slang term for a pungent or unpleasant smell.

Fusion reactor: A device that uses nuclear fusion to generate energy by fusing atomic nuclei.

Fusion: The process of combining nuclei to form a heavier nucleus and release energy.

Galactose: A monosaccharide sugar with the chemical formula C12H22O11, which is structurally similar to glucose and can be found in milk sugars and some glycoproteins.

Galvanic Cell: An electrochemical cell that converts chemical energy into electrical energy through spontaneous redox reactions.

Galvanic Cell: An electrochemical cell that converts chemical energy into electrical energy through an oxidation-reduction reaction, also known as a voltaic cell.

Galvanization: The process of coating iron or steel with a layer of zinc to protect against corrosion.

Gamma Decay: A type of radioactive decay in which an atomic nucleus emits a high-energy gamma photon, resulting in a change in energy levels of the nucleus.

Gamma Radiation: Electromagnetic radiation with high energy and short wavelength, emitted during gamma decay or other nuclear processes.

Gamma Radiation: High-energy electromagnetic radiation emitted during radioactive decay, with wavelengths shorter than X-rays.

Gamma-Hydroxybutyric Acid (GHB): A naturally occurring neurotransmitter and a psychoactive drug, with the chemical formula C4H8O2.

Gas Chromatography (GC): An analytical technique that separates volatile compounds in a mixture based on their partitioning between a mobile gas phase and a stationary phase on a column.

Gas Chromatography: A technique used to separate and analyze volatile compounds based on their distribution between a stationary phase and a mobile phase.

Gas Laws: A set of mathematical relationships describing the behavior of gases under different conditions of pressure, volume, and temperature.

Gas Laws: Principles that describe the behavior of gases, such as Boyle’s Law, Charles’s Law, Gay-Lussac’s Law, and Avogadro’s Law.

Gas Liquid Chromatography (GLC): A specific type of gas chromatography that uses a liquid stationary phase, often employed for separating volatile organic compounds.

Gas Phase: The physical state of a substance in which it exists as a gas, characterized by particles moving freely and having no fixed shape or volume.

Gas Solubility: The maximum amount of a gas that can dissolve in a liquid at a specific temperature and pressure, described by Henry’s Law.

Gas Turbine: A type of engine that uses a gas combustion process to produce rotational mechanical energy, often employed in aircraft and power generation.

Gas: A state of matter characterized by particles that are widely spaced and have high kinetic energy.

Gaseous Diffusion: The process by which gas molecules spread out and mix due to their kinetic energy and random motion.

Gauze: A porous, woven material, often made of cotton or other fibers, used in various applications such as filters, medical dressings, and supports in chemical reactions.

Geiger Counter: A device used to detect and measure ionizing radiation, often based on the ionization of gas molecules by radiation.

Gel Electrophoresis: A technique used to separate and analyze DNA, RNA, or proteins based on their size and charge in a gel matrix under an electric field.

Gel Permeation Chromatography (GPC): A type of size-exclusion chromatography used to separate molecules based on their hydrodynamic volume in solution.

Gel: A colloidal dispersion of a solid phase in a liquid medium, exhibiting properties of both solids and liquids.

Gel: A semi-solid material consisting of a network of particles suspended in a liquid, exhibiting liquid-like behavior under stress but retaining its shape.

Gelatinization: The process of swelling and softening of starch granules when heated in water, leading to the breakdown of their crystalline structure.

General Acidity: A measure of the ability of a substance to donate protons

Gibberellin: A plant hormone that regulates growth and development, particularly stem elongation and seed germination.

Gibbs Free Energy: A thermodynamic function that measures the maximum reversible work that can be done by a system at constant temperature and pressure.

Glass Transition Temperature: The temperature at which an amorphous polymer or glass transitions from a hard, brittle state to a softer, more flexible state.

Glass: An amorphous solid material formed by the rapid cooling of a molten substance, lacking a regular crystalline structure.

Glow Discharge: A low-pressure electrical discharge that produces a faint glow, often used in plasma-based analytical techniques like glow discharge optical emission spectroscopy (GD-OES).

Glucose: A monosaccharide sugar with the chemical formula C6H12O6, serving as a primary energy source for living organisms and a building block for more complex carbohydrates.

Glycerol: A colorless, viscous, and hygroscopic liquid used in various industrial and pharmaceutical applications, with the chemical formula C3H8O3.

Goldschmidt Classification: A classification system for elements based on their geochemical behavior and occurrence in Earth’s crust.

Goldschmidt’s Rule: A principle in geochemistry stating that the abundance of elements in the Earth’s crust is primarily determined by their atomic number.

Graft Copolymer: A copolymer formed by the attachment of polymer chains (grafts) onto a main polymer backbone.

Granule: A small, solid particle or clump, often used to describe solid materials in various industries and processes.

Graphite: A form of carbon consisting of layers of graphene arranged in a hexagonal lattice, used as a lubricant and electrode material.

Graphite: A form of carbon with a layered, hexagonal structure, characterized by its softness, lubricity,

Green Chemistry: The design of chemical processes and products that minimize environmental impact and maximize sustainability.

Grignard Reagent: An organometallic compound containing a carbon-magnesium bond, used as a versatile nucleophile in organic synthesis.

Ground State: The lowest energy state of an atom or molecule, with electrons occupying the lowest available energy levels.

Group: A column of elements in the periodic table sharing similar chemical properties due to the same number of valence electrons.

Halide: A negatively charged ion formed by the loss of a proton from a non-metal element, often found in Group 17 of the periodic table, such as chloride (Cl-) and iodide (I-).

Haloalkane: An organic compound containing one or more halogen atoms bonded to an alkyl group, such as chloroethane (CH3CH2Cl).

Haloaromatic: An aromatic organic compound containing one or more halogen atoms, like chlorobenzene (C6H5Cl).

Halogen: A group of highly reactive non-metal elements in Group 17 of the periodic table, including fluorine, chlorine, bromine, iodine, and astatine.

Hard Water: Water containing significant amounts of dissolved calcium and magnesium ions, which can cause scaling and reduce the effectiveness of soaps and detergents.

Headspace Analysis: A sample preparation technique for volatile organic compounds, involving the equilibration of analytes between a solid or liquid sample and the gaseous headspace above it.

Heat of Reaction: The amount of heat absorbed or released during a chemical reaction, quantified in joules or kilojoules per mole.

Heavy Water: A form of water containing the isotope deuterium (D2O) instead of the more common hydrogen isotope (H2O), used in research and nuclear reactors.

Henry’s Law: A principle in chemistry stating that the amount of a gas dissolved in a liquid is directly proportional to the partial pressure of the gas above the liquid, at a constant temperature.

Hess’s Law: A thermodynamic principle stating that the total enthalpy change of a reaction is the same, regardless of the pathway taken or the number of intermediate steps involved.

Heterogeneous Catalyst: A catalyst that is present in a different phase than the reactants, often in a solid form, like platinum on alumina in hydrogenation reactions.

Heterogeneous Equilibrium: A chemical equilibrium involving reactants and products in different phases, such as solid, liquid, and gas.

Heterogeneous Nucleation: The initial formation of a new phase in a system, involving nuclei with different compositions or structures than the surrounding material.

Heterolytic Bond Cleavage: The breaking of a bond in a molecule in such a way that the electrons are distributed between the two fragmenting atoms, leading to the formation of ions or polar molecules.

Heteropolyacids: Complex inorganic acids containing polyoxometalate anions, used as catalysts, catalyst supports, and in various industrial applications.

Hybridization: The blending of atomic orbitals to form new hybrid orbitals, which are used in the description of electron distribution in molecules.

Hydrate: A compound formed by the combination of a water molecule with another substance, such as ice hydrates in proteins or gas hydrates in geology.

Hydration Number: The number of water molecules associated with a specific ion in a solution, used to describe the degree of ion solvation.

Hydration State: The number of water molecules bound to an ion in a solution, influencing its chemical behavior and reactivity.

Hydration: The process of adding water molecules to a substance, often resulting in increased solubility or stability.

Hydridic Acidity: A measure of the ability of a molecule to donate protons, often used in the context of organohydrides and their acidity compared to water.

Hydrocarbon: An organic compound consisting entirely of hydrogen and carbon atoms

Hydrogen Bonding: A specific type of attractive interaction between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom, leading to the formation of hydrogen bonds in molecular systems.

Hydrogen Cation: A proton (H+) that acts as a cation in a chemical system.

Hydrogenation: A chemical reaction where hydrogen is added to a molecule, typically involving the reduction of a compound with the help of a catalyst.

Hydrolysis: A chemical reaction in which a molecule is cleaved into two parts by the addition of a water molecule, often used to describe the breakdown of covalent bonds.

Hydrometer: A device used to measure the specific gravity or density of a liquid, commonly employed in determining the alcohol content of liquids like wine and beer.

Hydropathy: A method in bioinformatics that uses hydrophobicity and hydrophilicity scales to predict the presence of alpha-helices and beta-sheets in proteins based on their amino acid sequences.

Hydrophilic: Describing a substance or region of a molecule that has an affinity for water, due to its polar nature and ability to form hydrogen bonds with water molecules.

Hydrophobic: Describing a substance or region of a molecule that does not mix with water, often due to its nonpolar nature and lack of hydrogen bonding capability.

Hydrostatic Pressure: The pressure exerted by a fluid at rest, depending on its depth and the density of the fluid.

Hypervalent Compound: A molecule containing an atom in a higher oxidation state than expected from its group number in the periodic table, often involving expanded or distorted electron orbitals.

Hypochlorite: A compound containing the chlorine ion (ClO-), such as sodium hypochlorite (NaClO), commonly used as a disinfectant and bleaching agent.

Indicator: A substance that changes color based on the pH of a solution, used to determine the endpoint of a titration.

Induction Period: The initial stage of a nucleation process, where no visible crystal growth occurs, preceding the rapid growth phase.

Inductive Effect: The influence of electron distribution in a molecule on the behavior of atoms or groups, caused by the buildup or withdrawal of electron density.

Inert Atmosphere: An environment devoid of reactive gases, often created using an inert gas like nitrogen or argon.

Inert Gas: A chemical element that is relatively unreactive due to a full valence electron shell, also known as noble gases.

Infrared Radiation: Electromagnetic radiation with wavelengths longer than visible light, often associated with heat transfer and molecular vibrations.

Inorganic Chemistry: The branch of chemistry that deals with the properties and reactions of substances that do not contain carbon-hydrogen bonds, typically involving metal elements and nonmetal elements or compounds.

Insoluble: Describing a substance that does not dissolve or dissolves very poorly in a given solvent.

Interfacial Tension: The force that acts along the boundary between two different phases, such as a liquid and a gas or two immiscible liquids.

Intermediate: A compound or species formed during a chemical reaction, often having a relatively short lifetime.

Intermolecular Forces: The forces of attraction or repulsion between molecules, such as van der Waals forces, hydrogen bonding, and ion-dipole interactions.

Internal Energy: The total energy contained within a system, including the kinetic and potential energy of its particles.

Interstellar Medium: The mixture of gas, dust, and cosmic radiation that fills the space between the star systems in the Milky Way and other galaxies.

Interstitial Compound: A compound formed by the insertion of atoms into the lattice structure of a metal crystal, resulting in a mixture of metal and nonmetal properties.

Iodine Clock Reaction: A classic chemical reaction used to demonstrate the effect of catalysts on reaction rates, involving the reaction between iodide ions and persulfate ions, with the addition of a catalyst significantly increasing the reaction rate.

Iodine: A chemical element with the symbol I and atomic number 53, a halogen essential for human health in trace amounts.

Ion Exchange: A process in which ions in a solution are exchanged for ions of the same charge on a solid ion exchange resin.

Ion Mobility Spectrometry: An analytical technique that separates ions based on their mobility in a gas, used for detecting and identifying gaseous ions.

Ion-Dipole Force: A type of intermolecular force between an ion and a polar molecule, where the ion is attracted to the polar molecule’s negatively charged region and vice versa, contributing to the stability of ionic compounds and molecular interactions.

Ion-Dipole Interaction: A type of electrostatic interaction between an ion and a polar molecule, where the positively charged ion is attracted to the negatively charged region of the polar molecule and vice versa, contributing to various chemical processes and molecular associations.

Ion-Dipole Interaction: A type of electrostatic interaction between an ion and a polar molecule, where the positively charged ion is attracted to the negatively charged region of the polar molecule and vice versa, contributing to various chemical processes

Ion-Exchange Resin: A porous, cross-linked polymer material containing ionizable functional groups, used for selectively exchanging ions in solution, a common application being water softening and purification.

Ionic Bond: A type of chemical bond formed between a metal and a nonmetal, resulting from the transfer of electrons from the metal to the nonmetal.

Ionic Bond: A type of chemical bond formed between a metal and a non-metal atom, resulting from the transfer of one or more electrons from the metal to the non-metal, leading to the formation of oppositely charged ions that are attracted to each other.

Ionic Compound: A compound formed from the combination of a metal and a nonmetal, resulting in an ionic bond and charged particles (ions).

Ionic Liquid: A salt with a melting point below 100°C, consisting of large, asymmetric ions that prevent crystallization.

Ionic Product of Water: The product of the concentration of hydrogen ions (H+) and hydroxide ions (OH-) in a solution, related to the pH and pOH values.

Ionic Product of Water: The product of the concentrations of hydrogen ions (H+) and hydroxide ions (OH-) in a solution, representing the balance between acidic and basic species in the solution and determining the pH value.

Ion-Ion Interaction: The electrostatic attraction or repulsion between two ions, depending on their charges, affecting the stability of ionic compounds, solvation, and electrolytic processes.

Ionization Energy: The energy required to remove an electron from an atom or ion, often expressed in electron volts (eV) or kilojoules per mole (kJ/mol).

Ionization Energy: The energy required to remove an electron from an atom or molecule in its gaseous state, determining the reactivity and stability of elements and compounds, and affecting chemical bonding and reaction mechanisms.

Ionization: The process of a neutral atom or molecule gaining or losing electrons to become an ion.

Ionization: The process of removing one or more electrons from an atom or molecule, resulting in the formation of an ion, typically requiring energy input and influenced by the molecule’s structure and the surrounding environment.

Ion-Pair: A temporary association between an ion and its counterion in a solution, resulting from electrostatic interactions, which can influence the solubility, conductivity, and reactivity of the ions.

Ion-Selective Electrode: An analytical device that measures the activity or concentration of a specific ion in a solution, by converting the ion’s concentration into an electrical signal, providing quantitative information about the ion’s presence.

Ion-Selective Membrane: A thin layer of material, typically a solid or liquid, that selectively allows the passage of specific ions based on their size, charge, or other properties, used in the construction of ion-selective electrodes and sensors.

Irreversible Reaction: A chemical reaction that does not proceed in the reverse direction under the same conditions,

Isobutane: A straight-chain alkane hydrocarbon isomer of butane, with a lower boiling point and higher vapor pressure, commonly used as a fuel, refrigerant, and aerosol propellant.

Isobutylene: An alkene hydrocarbon isomer of butene, with a more stable and less reactive structure due to the presence of two methyl groups adjacent to the double bond, leading to different chemical reactivity compared to other butenes.

Isocyanate: A functional group containing a nitrogen atom double-bonded to a carbon atom, with a lone pair of electrons available for nucleophilic attack, found in various organic compounds and used in the synthesis of urethane polymers.

Isocyanic Acid: A highly reactive and unstable compound with the molecular

Isoelectric Point: The pH at which an amphoteric molecule, like an amino acid or protein, carries no net charge due to the equal numbers of positively charged and negatively charged groups, affecting its solubility and behavior in solutions.

Isoelectronic Species: Two or more chemical species with the same number of electrons, leading to similar electronic configurations and properties, such as reactivity and bonding behavior.

Isoelectronic: Describing two or more atoms or ions with the same number of electrons, resulting in similar chemical behavior.

Isoenzymes: Different forms of an enzyme with the same catalytic activity but distinct structural properties, often arising from different genes or gene duplication events.

Isohydric Reaction: A reaction in which the total volume of the reactants and products remains constant, despite changes in their composition, typically observed in solvolysis reactions.

Isoindole: A heterocyclic aromatic organic compound containing a fused benzene ring and a five-membered ring with a nitrogen atom, found in various natural products and synthetic compounds.

Isomer: One of two or more species with the same chemical formula but different atomic arrangements, such as structural and stereoisomers.

Isomerism: The occurrence of two or more chemical species with the same molecular formula but different structural arrangements or spatial orientations, leading to distinct physical and chemical properties.

Isooctane: A hydrocarbon used as a reference standard in the octane rating system for gasoline fuels, having a high resistance to autoignition and providing a consistent basis for comparing the knock resistance of different fuels.

Isoquinoline: A heterocyclic aromatic organic compound containing a fused benzene ring and a five-membered ring with a nitrogen atom, found in various natural products and synthetic compounds.

Isothermal: Describing a process or system that occurs at a constant temperature.

Isotope: One of two or more forms of a chemical element, having the same atomic number but different mass numbers due to a different number of neutrons in the nucleus.

IUPAC: The International Union of Pure and Applied Chemistry, an organization responsible for establishing guidelines and rules in chemical nomenclature and terminology.

J-Aggregate Formation: The process of assembling chromophoric molecules into close arrangements, leading to unique spectroscopic properties and the formation of J-aggregates.

J-Aggregate Spectra: The absorption and emission spectra of J-

J-Aggregates: Specialized assemblies of chromophoric molecules, such as dyes or organic compounds, that exhibit unique spectroscopic properties due to their close arrangement and electronic coupling.

Jahnig-Labesche Rule: A principle in inorganic chemistry that predicts the stability of coordination complexes, stating that the number of d-electrons in a complex should not exceed the number of coordination spheres.

James-Martin Solution: A method for the continuous coulometric analysis of electroactive species in solution, involving the controlled generation and consumption of the analyte by an applied potential.

Janus Particles: Nanoparticles with two distinct surfaces or functionalities, named after the Roman god Janus who has two faces, useful in various applications such as drug delivery and surface patterning.

J-Band: A characteristic absorption band in Raman spectroscopy, corresponding to the in-plane vibrations of carbon atoms in graphene and other materials.

Joliot-Curie Effect: The phenomenon of artificially inducing radioactivity in an element by bombarding it with charged particles, named after the Joliot-Curie couple who discovered this effect.

Joliot-Curie Experiment: A pioneering experiment conducted by the Joliot-Curie couple, in which they bombarded boron with alpha particles, resulting in the discovery of artificial radioactivity and the production of the first radioactive isotope, boron-10.

Joliot-Curies: A family of French scientists, including Irene Joliot-Curie and her husband Frédéric Joliot-Curie, who made significant contributions to nuclear chemistry and radioactivity research.

Joule’s First Law: Also known as the conservation of energy principle, stating that the total energy in a closed system remains constant, as energy can neither be created nor destroyed, only converted from one form to another.

Joule’s Heat: The heat produced in a resistor due to the resistance of the material, resulting from the conversion of electrical energy to thermal energy as current passes through the resistor.

Joule’s Law of Heating: An alternative expression of Joule’s First Law, stating that the heat generated in an electrical resistor is proportional to the square of the current passing through it and the resistance of the resistor.

Joule’s Law: A principle in thermodynamics stating that the heat produced by an electric current passing through a resistor is proportional to the square of the current and the resistance, as well as the time the current flows.

Joule’s Second Law: A principle in thermodynamics stating that at equilibrium, all types of energy (kinetic, potential, etc.) are distributed equally among the available degrees of freedom in a system.

Joule’s Third Law: A proposed relationship between temperature and the thermodynamic properties of a substance, stating that the product of a substance’s entropy and its absolute temperature approaches a constant value as the temperature approaches absolute zero.

Joule-Thomson Effect: The phenomenon in which a gas experiences a temperature change when passing through a throttle valve, depending on the initial pressure and temperature conditions.

Joule-Thomson Expansion: The process of expanding a gas through a throttling valve without the application of external work, potentially leading to a temperature change due to the Joule-Thomson effect.

J-Type Thermocouple: A thermocouple with a positive temperature coefficient, meaning its output voltage increases with increasing temperature, suitable for measuring higher temperatures.

J-Type Thermoelectric Material: A material that exhibits a positive temperature coefficient in a thermoelectric device, where the output voltage increases with temperature, suitable for high-temperature applications.

Judd-Ofelt Theory: A method in the study of electronic spectra of rare-earth ions in solids, used to calculate the intensity of spectral lines and determine the crystal field parameters.

Junction Voltage: The voltage difference across a p-n junction in a semiconductor device, such as a diode, which is dependent on the junction’s properties and the applied external voltage.

J-Units: A unit of magnetic moment in atomic physics, equal to the product of the elemental charge and the classical electron radius.

J-Value Calculation: The process of determining the J-value ratio from experimental infrared spectra data to deduce molecular properties like force constants and reduced masses.

J-Value Determination: The process of calculating the J-value ratio in infrared spectroscopy to determine molecular properties like force constants and reduced masses.

J-Value Spectroscopy: A technique in infrared spectroscopy that involves the analysis of J-value ratios to study molecular properties and determine the nature of vibrational transitions.

J-Value: In infrared spectroscopy, the intensity ratio of two absorption bands corresponding to different vibrational quantum jumps, used to determine the force constant and reduced mass of a diatomic molecule.

Keggin Structure: A common anionic polyoxometalate structure, featuring a central atom surrounded by a ring of metal atoms and oxygen bridging ligands, commonly found in heteropolyacids and catalysts.

Kekulé Structure: A representation of the molecular structure of an organic compound, showing the arrangement of atoms and bonds in a planar or non-planar configuration, named after August Kekulé who proposed it.

Kerr Effect: A phenomenon in which the refractive index of a material changes due to the application of an external magnetic field, leading to the rotation of the plane of polarization of light passing through the material.

Keto-Enol Tautomerism: The reversible interconversion between a ketone and its corresponding enol form, an organic tautomerism involving the migration of a proton and the formation of a double bond between the carbonyl carbon and an adjacent carbon atom.

Ketone Resonance: In ketone molecules, the delocalization of electrons between the carbonyl carbon and oxygen atoms, resulting in the formation of resonance structures and increased stability.

Ketone: A type of organic compound containing a carbonyl group (C=O) bonded to two other carbon or hydrogen atoms, with the general formula RCOR’.

Kinetic Chain Length in Polymerization: The number of elementary steps or reactions required for the formation of a polymer molecule, influencing the overall reaction rate and efficiency.

Kinetic Energy: The energy possessed by an object due to its motion, directly proportional to its mass and the square of its velocity, and inversely proportional to the mass of a stationary object.

Kinetic Isotope Effect: The observation that the rate of a chemical reaction may be influenced by the isotopic composition of the reacting molecules, due to the differences in their atomic masses affecting the reaction’s energy barriers.

Kinetic Molecular Theory: A set of principles describing the behavior of gases based on the assumption that gas molecules are in constant motion and collide with each other and the walls of their container, leading to pressure and temperature changes.

Kinetic Theory of Gases: A theoretical framework that describes the behavior of gases in terms of the motion and collisions of their constituent particles, providing explanations for gas laws and properties.

Kinetics of Radiation-Induced Reactions: The study of the rates and mechanisms of chemical reactions initiated by ionizing radiation, such as X-rays, gamma rays, or particle bomb

Kinetics of Reactions: The study of the rates at which chemical reactions occur, including factors affecting reaction rates, reaction mechanisms, and the mathematical models used to describe reaction progress.

Kinetics: The branch of chemistry that deals with the study of reaction rates, reaction mechanisms, and the factors affecting them, focusing on the time-dependent behavior of chemical systems.

Knoevenagel Condensation: A condensation reaction in organic chemistry involving the formation of a γ-ketoaldehyde or γ-ketoacid from a carbonyl compound and an active methylene compound in the presence of a base.

Kohlrausch’s Law: A principle in electrochemistry stating that the apparent molar conductivity of an electrolyte solution is the sum of the molar conductivities of its individual ions, considering their concentrations and the ionic strength of the solution.

Kossel’s Rule: A principle in crystal chemistry stating that the coordination number of an ion in a crystal lattice is determined by the balance between the electrostatic attraction to the surrounding anions and the repulsion from the neighboring cations.

Krebs Cycle: A series of biochemical reactions in cellular respiration, also known as the citric acid cycle or TCA cycle, responsible for generating energy in the form of ATP and releasing waste products like CO2 and H2O.

Krohnke’s Rule: A rule in inorganic chemistry that predicts the stability of metal carbonyl complexes, stating that the number of carbon monoxide ligands bound to a metal center is equal to the number of available coordination sites minus one.

Kugelblitz: A hypothetical, extremely fast process in quantum mechanics, where a particle accelerates so rapidly that it forms a black hole before interacting with other particles, preventing the emission of electromagnetic radiation.

Kuhn’s Structural Theory: A theory in chemistry proposed by Hans Kuhn, suggesting that the structure of macromolecules like proteins and nucleic acids is determined by the arrangement of their constituent monomers and the interactions between them, rather than being solely dictated by the primary sequence.

Labile Compound: A chemically unstable compound that easily decomposes or undergoes chemical reactions.

Lactam: A cyclic amide containing a nitrogen atom and an amide group, found in various natural products and synthetic polymers like nylon.

Lactone: A cyclic ester with a carbonyl group and an alcohol group, found in various natural products and synthetic compounds.

Lagrangian Mechanics: A branch of classical mechanics that uses the Lagrangian function to describe the motion of a system in terms of generalized coordinates and their derivatives.

Laminar Flow: A smooth, non-turbulent flow of a fluid, characterized by parallel layers moving at different velocities.

Langmuir Adsorption: A model describing the adsorption of molecules onto a surface, based on the formation of a monolayer with specific adsorption sites.

Lanthanide Series: A group of 15 elements in the periodic table from lanthanum (La) to lutetium (Lu), characterized by the filling of 4f orbitals.

Lanthanides: A series of 15 elements in the periodic table, also known as rare earth elements, with atomic numbers 57-71 (from lutetium to lutetium).

Laser: A device that produces a highly monochromatic, coherent, and intense beam of light through the stimulated emission of photons in a laser medium.

Latent Heat of Fusion: The heat required to change a substance from its solid phase to its liquid phase at constant temperature, without any change in internal energy.

Latent Heat of Vaporization: The heat required to change a substance from its liquid phase to its gas phase at constant temperature, without any change in internal energy.

Latent Heat: The heat absorbed or released by a substance during a phase transition at constant temperature, without a change in its internal energy.

Latent Image: An invisible image formed in photographic film or paper due to the redistribution of silver halide particles, which becomes visible after chemical development.

Lattice Defect: An irregularity or imperfection in the regular arrangement of atoms or ions in a crystal lattice, including vacancies, interstitials, and dislocations.

Lattice Energy: The energy released when ions in the gaseous state come together to form a solid ionic compound, measured in kilojoules per mole (kJ/mol).

Lattice Energy: The energy released when ions in the gaseous state come together to form a solid ionic compound, measured in kilojoules per mole (kJ/mol).

Lattice Energy: The energy required to separate one mole of ions in a solid ionic compound into gaseous ions, measured in kilojoules per mole (kJ/mol).

Lattice Matched: Referring to the alignment of crystal lattices between two materials, minimizing lattice strain and defects at the interface.

Lattice Parameter: A characteristic length scale of a crystal lattice, typically the distance between adjacent lattice points in a crystal structure.

Lattice Point: A position in a crystal lattice occupied by an atom, ion, or molecule.

Lattice: A regular arrangement of atoms, ions, or molecules in a crystalline solid, forming repeating unit cells.

Law of Conservation of Mass: The principle stating that the total mass of reactants in a chemical reaction is equal to the total mass of products, with no loss or gain of mass.

Laws of Thermodynamics: A set of fundamental principles governing the behavior of energy and matter in physical and chemical systems, including conservation of energy, entropy, and absolute temperature.

Le Chatelier’s Principle: A principle in chemical equilibrium that states when a system at equilibrium is subjected to a change in concentration, temperature, or pressure, it will adjust to counteract the change and restore a new equilibrium.

Le Chatelier’s Principle: A principle in chemical equilibrium that states when a system at equilibrium is subjected to a change in concentration, temperature, or pressure, it will adjust to counteract the change and restore a new equilibrium.

Le Chatelier’s Principle: The principle stating that if a system at equilibrium is subjected to a stress, it will respond by shifting the equilibrium to minimize the effect of the stress.

Least Squares Fitting: A statistical method used in chemistry and other sciences to determine the best-fit line or curve through a set of data points by minimizing the sum of the squares of the residuals.

Leukocyte: A type of white blood cell involved in immune responses and defense against pathogens, including neutrophils, lymphocytes, and monocytes.

Lever Rule: A method used in phase diagrams and chemical equilibrium to determine the composition of a mixture in a two-phase region based on the relative amounts of the phases present.

Lewis Acid: A chemical species that can accept a pair of electrons to form a covalent bond, according to Lewis acid-base theory.

Lewis Acid: A chemical species that can accept a pair of electrons to form a covalent bond, according to Lewis acid-base theory.

Lewis Acid: A substance that accepts electron

Lewis Base: A chemical species that can donate a pair of electrons to form a covalent bond, according to Lewis acid-base theory.

Lewis Structure: A diagram that represents the bonding and electron distribution in a molecule or ion using dots to represent valence electrons and lines to represent covalent bonds.

Ligand Exchange: A process in which a ligand in a coordination complex is replaced by another ligand, often facilitated by a change in the reaction conditions or the addition of a suitable reagent.

Ligand Field Splitting: The splitting of the energy levels of the d-orbitals in a transition metal ion due to the interaction with surrounding ligands, leading to different electronic configurations and colors in coordination compounds.

Ligand Field Theory: A quantum mechanical approach to describe the electronic structure of transition metal complexes, taking into account the interaction between the central metal ion and the surrounding ligands.

Ligand Field Theory: A theory that describes the electronic structure and magnetic properties of coordination complexes based on the interaction between metal d orbitals and ligand orbitals.

Ligand: A molecule or ion that binds to a central metal atom or ion in a coordination complex, forming a coordination compound.

Ligand: A molecule or ion that binds to a central metal ion or atom in a coordination complex through coordinate covalent bonds.

Light Absorption: The process by which a substance, such as a molecule or a material, takes in photons and converts them into other forms of energy, such as heat or chemical energy.

Light Emission: The process by which a substance releases energy in the form of photons, resulting in the production of visible or non-visible light.

Light-Harvesting Complex: A specialized protein-pigment complex in photosynthetic organisms that captures and transfers light energy to the reaction center, where the energy conversion to chemical energy occurs.

Limiting Reactant: The reactant in a chemical reaction that is completely consumed before the reaction reaches completion, thus determining the maximum amount of product that can be formed.

Limiting Reactant: The reactant that is completely consumed in a chemical reaction, determining the maximum amount of product that can be formed.

Lindlar Catalyst: A palladium catalyst poisoned with lead or quinoline used for the selective hydrogenation of alkynes to cis-alkenes.

Line Broadening: The increase in the width of a spectral line due to various factors, such as Doppler broadening, pressure broadening, or collision broadening, which cause the line to lose its sharpness and merge with neighboring lines.

Line Spectroscopy: A technique in spectroscopy that involves analyzing the absorption or emission of light at specific wavelengths or lines, often used to study atomic or molecular energy levels and identify elements or compounds.

Linear Combination of Atomic Orbitals (LCAO): A method used in molecular orbital theory to construct molecular orbitals from linear combinations of atomic orbitals, providing a qualitative description of bonding and antibonding interactions in molecules.

Linear Dichroism: The differential absorption of light polarized along different axes in a molecular or crystalline sample, providing information about the orientation and alignment of molecules or chromophores within the sample.

Linear Free Energy Relationship: A relationship between the rate or equilibrium constant of a chemical reaction and a measure of the reactants’ or products’ free energy, often used to predict reaction outcomes or optimize reaction conditions.

Linear Molecule: A molecule in which all atoms are arranged in a straight line, often with bond angles of 180 degrees.

Linear Sweep Voltammetry: An electroanalytical technique in which the potential of a working electrode is varied linearly with time, allowing the measurement of current as a function of potential and providing information about redox processes and electrode kinetics.

Lipid Bilayer: A double layer of lipid molecules that forms the basic structure of cell membranes, with hydrophilic heads facing outward and hydrophobic tails facing inward.

Lipid: A diverse group of organic compounds including fats, oils, phospholipids, and steroids, characterized by their insolubility in water and role in energy storage and cell membrane structure.

Lipophilic: Having an affinity for lipids or nonpolar solvents, often used to describe molecules that readily dissolve in fats.

Lipophilicity: A measure of a molecule’s affinity for lipid environments, such as cell membranes or organic solvents, often described by its

Lipophilicity: The tendency of a compound to dissolve in lipids or nonpolar solvents, often related to its partition coefficient between water and octanol.

Liposome: A spherical vesicle composed of a lipid bilayer, used as a carrier for drugs or other molecules in pharmaceutical and biotechnological applications.

Liposome: A spherical vesicle composed of one or more phospholipid bilayers, used in drug delivery systems and as models for studying cell membrane properties and functions.

Liquefaction: The process of converting a gas or vapor into a liquid state, typically by cooling or increasing pressure.

Liquid Chromatography (LC): A widely used analytical technique for separating and analyzing mixtures of compounds based on their differential distribution between a mobile phase (liquid) and a stationary phase (solid).

Liquid Crystal: A substance that exhibits properties between those of conventional liquids and solid crystals, displaying long-range order in their molecular arrangement but lacking the rigid, three-dimensional structure of a crystal lattice.

Liquid Crystals: Materials with properties intermediate between those of a liquid and a solid, often exhibiting ordered molecular arrangements.

Liquid-Liquid Extraction: A separation technique based on the partitioning of solutes between two immiscible liquid phases, often used in purification and isolation processes.

Liquid-Liquid Extraction: A separation technique in which a solute is selectively transferred from one liquid phase to another immiscible liquid phase, based on differences in their solubility in the two phases.

Liquid-Solid Equilibrium: The state of thermodynamic equilibrium between a liquid phase and a solid phase of a substance, characterized by a constant temperature and pressure.

Liquid-Vapor Equilibrium: The state of thermodynamic equilibrium between a liquid phase and a vapor phase of a substance, characterized by a constant temperature and pressure.

Lithium-Ion Battery: A type of rechargeable battery that uses lithium ions moving between the anode and cathode during charging and discharging, providing high energy density and long cycle life.

Living Polymerization: A controlled polymerization technique that allows the formation of polymers with well-defined molecular weight distributions and end-group functionalities, essential for creating block copolymers and well-defined macromolecular architectures.

Localized Orbital: A molecular orbital that is confined to a specific region or atom in a molecule, resulting in a well-defined chemical bond or orbital interaction.

Lone Pair: A pair of valence electrons that are not involved in bonding and are localized on an atom, often represented as a pair of dots in Lewis structures.

Lone Pair: A pair of valence electrons that are not involved in bonding and are localized on an atom, often represented as a pair of dots in Lewis structures.

Long-Chain Fatty Acid: A fatty acid with a carbon chain length greater than 12 carbons, often found in natural fats and oils, and used in the synthesis of soaps, detergents, and other surfactants.

Longitudinal Magnetic Resonance (LMR): A type of nuclear magnetic resonance (NMR) technique that measures the resonance of nuclei along the direction of the applied magnetic field, providing information about the magnetic susceptibility and molecular dynamics of

Luminescence: The emission of light by a substance not resulting from incandescence, often due to electronic transitions within the molecule.

Luminescent Dye: A fluorescent or phosphorescent compound used to label or stain biomolecules for detection and imaging purposes.

Lyophilic Colloid: A colloidal dispersion in which the dispersed phase has a strong affinity for the dispersion medium, resulting in stable colloidal particles.

Lyophilic Colloid: A colloidal dispersion in which the dispersed phase has a strong affinity for the dispersion medium, resulting in stable colloidal particles.

Lyophilization: A process of freeze-drying or drying by sublimation to remove water from a substance while preserving its structure and properties.

Lyophobic Colloid: A colloidal dispersion in which the dispersed phase has little or no affinity for the dispersion medium, requiring stabilizing agents to prevent coagulation.

Lyophobic Colloid: A colloidal dispersion in which the dispersed phase has little or no affinity for the dispersion medium, requiring stabilizing agents to prevent coagulation.

Macromolecule: A large molecule, typically composed of repeating structural units, such as proteins, nucleic acids, and polysaccharides, which play essential roles in biological systems and materials science.

Magnetic Quantum Number: A quantum number that specifies the orientation of an orbital within a subshell, ranging from -l to +l.

Magnetic Resonance Imaging (MRI): A non-invasive diagnostic imaging technique that utilizes the principles of nuclear magnetic resonance (NMR) to generate detailed images of the internal structures of the body, based on the relaxation times of hydrogen nuclei in tissues.

Magnetic Resonance Spectroscopy (MRS): A technique that uses the principles of nuclear magnetic resonance (NMR) to study the chemical composition, molecular interactions, and dynamic processes in biological systems, materials, and chemical reactions.

Malachite Green: A triphenylmethane dye used as a textile dye, food colorant, and biocide, known for its bright green color and potential toxicity to aquatic life.

Malondialdehyde (MDA): A reactive aldehyde formed as a byproduct of lipid peroxidation, often used as a biomarker for oxidative stress and cellular damage.

Mandelic Acid: An organic acid derived from the amino acid phenylalanine, used as an intermediate in the synthesis of various chemicals, a topical antioxidant, and in some skincare products.

Marcus Theory: A theoretical framework in physical chemistry that describes the rate of electron transfer reactions, taking into account the reorganization energy of the system and the coupling between the reactants and products.

Mass Action Law: A principle in chemical kinetics that states the rate of a chemical reaction is proportional to the product of the concentrations of the reactants, each raised to the power of their stoichiometric coefficients.

Mass Number: The total number of protons and neutrons in the nucleus of an atom, used to identify isotopes of an element.

Mass Spectrometer: An analytical instrument used to measure the mass-to-charge ratio of ions, providing information about the molecular weight and structure of compounds.

Mass Spectrometer: An instrument that produces and analyzes ions based on their mass-to-charge ratio, used in conjunction with chromatography or other separation techniques to identify and quantify compounds in complex mixtures.

Mass Spectrometry (MS): An analytical technique that measures the mass-to-charge ratio of ions to identify and quantify the components of a mixture, widely used in chemistry, biology, and environmental science.

Mass Spectrometry: An analytical technique used to determine the molecular weight and structural information of compounds based on the mass-to-charge ratio of ions.

Melting Point: The temperature at which a solid substance changes to a liquid state at atmospheric pressure.

Melting Point: The temperature at which a solid substance changes to a liquid state at atmospheric pressure.

Metal Complex: A coordination compound consisting of a central metal ion or atom bonded to surrounding ligands through coordinate covalent bonds.

Metal Complex: A coordination compound consisting of a central metal ion or atom bonded to surrounding ligands through coordinate covalent bonds.

Metal: An element characterized by its luster, conductivity, malleability, and ductility, typically found on the left side of the periodic table.

Metallic Bonding: The electrostatic attraction between positively charged metal ions and delocalized electrons in a metal lattice.

Metalloid: An element with properties intermediate between those of metals and nonmetals, located along the diagonal line on the periodic table.

Metalloid: An element with properties intermediate between those of metals and nonmetals, located along the diagonal line on the periodic table.

Micelle: A colloidal structure formed by aggregation of amphiphilic molecules in a solution, with hydrophobic tails pointing inward and hydrophilic heads outward.

Micelle: A colloidal structure formed by aggregation of amphiphilic molecules in a solution, with hydrophobic tails pointing inward and hydrophilic heads outward.

Molal Freezing Point Depression Constant: A constant representing the degree to which the freezing point of a solvent is lowered by the addition of a nonvolatile solute, expressed in degrees Celsius per molal (°C/m).

Molality: A measure of concentration representing the number of moles of solute dissolved in one kilogram of solvent.

Molality: A measure of concentration representing the number of moles of solute dissolved in one kilogram of solvent.

Molality: A measure of concentration representing the number of moles of solute dissolved in one kilogram of solvent.

Molar Absorptivity: A measure of the ability of a substance to absorb light at a specific wavelength, expressed in units of liters per mole per centimeter (L/mol/cm).

Molar Absorptivity: A measure of the ability of a substance to absorb light at a specific wavelength, expressed in units of liters per mole per centimeter (L/mol/cm).

Molar Conductivity: The conductivity of a solution containing one mole of solute dissolved in one liter of solution, measured in siemens per meter (S/m).

Molar Conductivity: The conductivity of a solution containing one mole of solute dissolved in one liter of solution, measured in siemens per meter (S/m).

Molar Heat Capacity: The amount of heat energy required to raise the temperature of one mole of a substance by one degree Celsius or one Kelvin.

Molar Heat Capacity: The amount of heat energy required to raise the temperature of one mole of a substance by one degree Celsius or one Kelvin.

Molar Mass: The mass of one mole of a substance, expressed in grams per mole (g/mol).

Molar Volume: The volume occupied by one mole of a substance at a specific temperature and pressure, typically expressed in liters per mole (L/mol).

Molar Volume: The volume occupied by one mole of a substance at a specific temperature and pressure, typically expressed in liters per mole (L/mol).

Molarity: A measure of concentration representing the number of moles of solute dissolved in one liter of solution.

Molarity: A measure of concentration representing the number of moles of solute dissolved in one liter of solution.

Mole Fraction: The ratio of the number of moles of a component to the total number of moles in a mixture.

Mole: A unit of measurement used in chemistry to express the amount of a substance, equal to approximately 6.022 x 10^23 entities.

Molecular Formula: A chemical formula that represents the exact number of each type of atom present in a molecule.

Molecular Formula: A chemical formula that represents the exact number of each type of atom present in a molecule.

Molecular Orbital Theory: A theory that describes the behavior of electrons in molecules by considering the overlap of atomic orbitals to form molecular orbitals.

Molecular Orbital Theory: A theory that describes the behavior of electrons in molecules by considering the overlap of atomic orbitals to form molecular orbitals.

Molecular Sieve: A porous material used to separate molecules based on size and shape, often employed in gas chromatography and dehydration processes.

Molecular Weight: The sum of the atomic weights of all atoms in a molecule, expressed in atomic mass units (amu) or grams per mole (g/mol).

Molecular Weight: The sum of the atomic weights of all atoms in a molecule, expressed in atomic mass units (amu) or grams per mole (g/mol).

Monomer: A small molecule that can undergo polymerization to form a larger polymer chain.

Monomer: A small molecule that can undergo polymerization to form a larger polymer chain.

Nanobiotechnology: The application of nanotechnology to the field of biology, including the development of nanomaterials for biomedical applications.

Nanocatalysis: The use of nanomaterials as catalysts to accelerate chemical reactions, often with improved efficiency and selectivity.

Nanomaterial: A material with dimensions on the nanometer scale, often exhibiting unique properties due to their small size.

Nanoparticle: A particle with dimensions in the nanometer range, typically consisting of a few to thousands of atoms or molecules.

Nanoparticle: A tiny particle with dimensions in the nanometer range (1-100 nm), often exhibiting unique physical, chemical, and biological properties due to their high surface-to-volume ratio and quantum confinement effects.

Nanoparticle: A tiny particle with dimensions on the nanometer scale, often used in nanotechnology and materials science.

Nanoporous: Refers to materials or structures containing nanoscale pores or voids, often used in adsorption, catalysis, and separation processes.

Nanotechnology: The branch of science and engineering that deals with the manipulation of matter on the nanometer scale.

Naphthalene: A white crystalline aromatic hydrocarbon, commonly used as a moth repellent and in the production of dyes and resins.

Naphthol: A group of isomeric aromatic alcohols derived from naphthalene, often used as dyes, antioxidants, and intermediates in organic synthesis.

Nernst Distribution Law: A law describing the distribution of solute between two immiscible solvents in equilibrium.

Nernst Equation: A relationship between the electrochemical potential of a redox couple (half-cell reaction) and the standard electrode potential, temperature, and concentrations of the species involved, used to determine the cell potential under non-standard conditions.

Nernst Equation: An equation used to calculate the equilibrium potential of an electrochemical cell under non-standard conditions.

Nernstian Slope: The slope of the potential-pH relationship for an electrochemical reaction, typically equal to 59.16 mV/decade at 25°C, reflecting the Nernst equation’s dependence on the concentrations of the reactants and products.

Neutralization: The chemical reaction between an acid and a base to produce salt and water.

Neutron Activation Analysis: An analytical technique used to determine the elemental composition of a sample by bombarding it with neutrons and measuring the resulting gamma radiation.

Neutron: A subatomic particle found in the nucleus of an atom, with no electrical charge but a mass similar to that of a proton.

Nitrate: An inorganic ion (NO3-) derived from nitric acid, often found in fertilizers, explosives, and environmental pollutants.

Nitration: The chemical process of introducing a nitro group (NO2) into a molecule.

Nitric Acid (HNO3): A strong inorganic acid, widely used in the production of fertilizers, explosives, and various chemicals, as well as in air quality monitoring and automotive emissions control.

Nitriding: A surface hardening process in which nitrogen is diffused into the surface of a metal to improve hardness, wear resistance, and corrosion resistance.

Nitriding: A surface treatment process that enhances the corrosion resistance, hardness, and wear resistance of metals by introducing nitrogen into the surface layers, typically through exposure to ammonia or nitrogen-containing gases at elevated temperatures.

Nitro Group: A functional group (-NO2) consisting of a nitrogen atom bonded to two oxygen atoms, often found in explosives and pharmaceuticals.

Nitroaromatic Compounds: Aromatic compounds containing one or more nitro groups (-NO2) attached to the aromatic ring, exhibiting various chemical and physical properties, and found in explosives, dyes, and environmental pollutants.

Nitrocellulose: A highly flammable, cellulose-based material containing nitrate ester groups, used as a film base in photography, a binder in lacquers and varnishes, and as a plasticizer in gunpowder.

Nitrogen Fixation: The biological or industrial process of converting atmospheric nitrogen gas into ammonia or other nitrogen-containing compounds.

Nitrogen Fixation: The process by which atmospheric nitrogen (N2) is converted into biologically available forms, such as ammonia (NH3) or ammonium ions (NH4+), through biological (e.g., nitrogen-fixing bacteria) or industrial (e.g., Haber-Bosch process) processes.

Nitrogen Gas: A diatomic gas (N2) that constitutes approximately 78% of Earth’s atmosphere, used in various industrial applications, as an inert atmosphere for chemical reactions, and as a coolant in cryogenics.

Nitrogen Oxides (NOx): A group of nitrogen-oxygen compounds, including nitric oxide (NO) and nitrogen dioxide (NO2), produced by combustion processes and air pollution.

Nitrogenase: A complex enzyme system responsible for biological nitrogen fixation, catalyzing the reduction of atmospheric nitrogen to ammonia or other biologically available forms.

Noble Gas Configuration: A stable electron configuration resembling that of the noble gases, characterized by a filled valence shell.

Noble Gas: An element in Group 18 of the periodic table, characterized by its full outer electron shell and inertness.

Noble Metal: A metal resistant to oxidation and corrosion, including gold, platinum, and palladium, often used in jewelry and catalysis.

Nonmetal: An element characterized by its lack of metallic properties, typically found on the right side of the periodic table.

Nonvolatile: Refers to substances that have low vapor pressure and do not readily evaporate at normal temperatures, such as oils and polymers.

Nuclear Fission: The process by which a heavy nucleus splits into smaller nuclei, releasing a large amount of energy, used in nuclear power plants and atomic bombs.

Nuclear Fusion: The process by which atomic nuclei combine to form heavier nuclei, releasing energy in the Sun and stars.

Nuclear Isomer: Isomeric forms of atomic nuclei with the same atomic number and mass number but different nuclear energy states and lifetimes.

Nuclear Magnetic Resonance (NMR): A spectroscopic technique used to determine the structure and dynamics of molecules based on the interaction of atomic nuclei with a strong magnetic field.

Nuclear Magnetic Resonance Spectroscopy (NMR): A powerful analytical technique used to study the structure, composition, and dynamics of molecules based on their interaction with magnetic fields.

Nuclear Radiation: Emission of particles or electromagnetic radiation from atomic nuclei during radioactive decay processes.

Nuclear Reactor: A device that initiates and controls nuclear reactions to generate energy, commonly used in nuclear power plants.

Nuclear Shell Model: A model that describes the arrangement of nucleons (protons and neutrons) in atomic nuclei based on energy levels and quantum numbers.

Nucleation: The initial stage of phase transition in which tiny clusters of atoms or molecules aggregate to form nuclei of the new phase.

Nucleophile: A chemical species that donates an electron pair to form a covalent bond with an electron-deficient atom or center.

Nucleophile: A chemical species with a lone pair of electrons that can donate to a positively charged atom (electrophile) in a chemical reaction, promoting the formation of a new bond and driving the reaction forward.

Nucleophilic Addition: A type of organic reaction in which a nucleophile adds to the carbon-carbon double or triple bond of an unsaturated compound.

Nucleophilic Alylation: A reaction in which an alkene or alkyne reacts with an alkyl halide in the presence of a metal catalyst and a nucleophile, resulting in the formation of a new C-C bond and the migration of an alkyl group.

Nucleophilic Aromatic Substitution: A reaction mechanism in which a nucleophile attacks an aromatic ring, leading to the formation of a new bond and the displacement of a leaving group, preserving the aromaticity of the ring.

Nucleophilic Catalytic Aromatic Substitution: A reaction mechanism involving the use of a nucleophile and a catalyst to promote aromatic substitution, allowing for the formation of products that may not be possible through other reaction pathways.

Nucleophilic Epoxidation: A reaction in which an epoxide ring is opened by a nucleophile, often in the presence of an acid or base catalyst, leading to the formation of various functionalized alcohols and other products.

Nucleophilic Rearrangement: A chemical reaction in which a nucleophile attacks a substrate, leading to the migration of an alkyl or aryl group and the formation of a new bond, often accompanied by the cleavage of a bond and the generation of a new functional group.

Nucleophilic Substitution: A class of chemical reactions in which a nucleophile replaces a leaving group in a molecule, leading to the formation of new bonds and the displacement of the leaving group.

Nucleophilic Substitution: A type of organic reaction in which a nucleophile replaces a leaving group on a carbon atom.

Nucleoside: A fundamental building block of nucleic acids (DNA and RNA), consisting of a nitrogenous base and a sugar (ribose or deoxyribose) linked together by a covalent bond.

Nucleoside: A molecule consisting of a nitrogenous base (purine or pyrimidine) linked to a sugar molecule (ribose or deoxyribose).

Nucleotide: The building block of nucleic acids (DNA and RNA), consisting of a nitrogenous base, a sugar molecule, and a phosphate group.

Nucleotide: The monomeric unit of nucleic acids, composed of a nucleoside and one or more phosphate groups, forming the structural and functional units of DNA, RNA, and other cellular processes.

Nucleus: The central part of an atom containing protons and neutrons, with electrons orbiting around it.

Octane: A hydrocarbon (C8H18) found in gasoline, used as a measure of fuel quality and knock resistance in internal combustion engines, with higher octane numbers indicating better performance and reduced engine knocking.

Octet Rule: A rule stating that atoms tend to gain, lose, or share electrons to achieve a stable configuration with eight valence electrons.

Octet Rule: The principle stating that atoms tend to gain, lose, or share electrons to achieve a stable configuration with eight valence electrons.

Olefin Metathesis: A class of reactions in which carbon-carbon double bonds (C=C) in olefin molecules are rearranged and exchanged, creating new carbon-carbon double bonds and forming a variety of unsaturated organic compounds.

Oligosaccharide: A carbohydrate consisting of a few monosaccharide units joined by glycosidic bonds.

Optical Isomerism: Stereoisomerism arising from the arrangement of atoms or groups around an asymmetric carbon atom, resulting in non-superimposable mirror images.

Optical Isomerism: Stereoisomerism in which molecules have the same molecular formula and connectivity but differ in spatial arrangement, resulting in different optical properties.

Orbital: A region of space around the nucleus of an atom where an electron is likely to be found.

Organic Chemistry: The branch of chemistry dealing with compounds containing carbon atoms, often studied in relation to their structure, properties, and reactions.

Organic Chemistry: The branch of chemistry that deals with the study of carbon-containing compounds, including hydrocarbons and their derivatives.

Organic Synthesis: The construction of organic compounds using chemical reactions, often with the goal of designing new molecules with specific properties.

Organic Synthesis: The process of building organic compounds from simpler starting materials through chemical reactions.

Organometallic Compound: A compound containing at least one metal-carbon bond, often used as catalysts in organic synthesis.

Organometallic: Compounds containing at least one metal-to-carbon bond.

Ortho-Compound: A type of substitution pattern in aromatic compounds where substituent groups are adjacent to each other on the benzene ring.

Orthogonal: Referring to molecules or functional groups that are spatially independent and do not interfere with each other’s reactions.

Ortho-Quinone: A type of compound containing a quinone functional group, characterized by two carbonyl groups adjacent to each other on a benzene ring.

Osmosis: The movement of solvent molecules through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Osmosis: The movement of solvent molecules through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.

Osmosis: The passive movement of solvent molecules (usually water) through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration, driven by a difference in osmotic pressure.

Osmotic Pressure: The pressure required to prevent or reverse osmosis by reducing the concentration gradient across a semipermeable membrane, related to the solute concentration and the temperature through the van’t Hoff equation.

Oxaloacetic Acid: A four-carbon organic acid involved in the citric acid cycle, serving as an intermediate in energy metabolism.

Oxazole: A five-membered aromatic heterocycle containing one oxygen and one nitrogen atom in the ring.

Oxidation Number: A concept representing the charge an atom would have if electrons were transferred completely, based on certain rules.

Oxidation Number: A method of assigning an integer charge to each atom in a molecule or ion, based on the number of electrons that the atom would need to transfer to or accept from other atoms to achieve a stable electron configuration, used to determine the balanced oxidation state of elements in a compound.

Oxidation Potential: The tendency of a substance to undergo oxidation, measured in volts under standard conditions.

Oxidation State: A measure of the degree of oxidation of an atom in a chemical compound, indicating the number of electrons it has gained or lost.

Oxidation State: The hypothetical charge an atom would have if all its bonds were completely ionic.

Oxidation: A chemical process in which an atom, ion, or molecule loses electrons, resulting in an increase in oxidation state, often accompanied by the formation of new functional groups or the cleavage of chemical bonds.

Oxidation: The loss of electrons by a chemical species, resulting in an increase in oxidation state.

Oxidation: The process of losing electrons or gaining oxygen, often accompanied by an increase in oxidation state.

Oxidation-Reduction Reaction (Redox): A chemical reaction involving the transfer of electrons between reactants, resulting in changes in oxidation states.

Oxidation-Reduction Reaction: A chemical reaction involving the transfer of electrons between reactants.

Oxidative Coupling: A chemical reaction in which two molecules are joined together with the simultaneous loss of electrons, often used in polymerization reactions.

Oxidative Deamination: The removal of an amino group from an amino acid, resulting in the formation of ammonia and a keto acid.

Oxidative Phosphorylation: The process in cellular respiration where ATP is synthesized using energy derived from the transfer of electrons in the electron transport chain.

Oxidative Phosphorylation: The process in cellular respiration where ATP is synthesized using energy released by electron transport chain.

Oxidative Stress: An imbalance between the production of reactive oxygen species (ROS) and the ability of cells to detoxify them, leading to cellular damage.

Oxidative Stress: Cellular damage caused by an imbalance between the production of reactive oxygen species (ROS) and the body’s ability to detoxify them.

Oxide: A compound containing oxygen atoms bonded to another element, such as carbon dioxide (CO2) or iron oxide (Fe2O3).

Oxidizing Agent: A chemical species that accepts electrons in a redox reaction, causing another substance to be oxidized.

Oxidizing Agent: A chemical species that gains electrons during a redox reaction, causing the oxidation of another species (the reducing agent), and is itself reduced in the process.

Oxidizing Agent: A substance that causes oxidation in another substance by accepting electrons or removing hydrogen.

Oxime: A compound containing the functional group -C=N-OH, formed by the reaction of hydroxylamine with aldehydes or ketones.

Oxygen Gas (O2): A diatomic gas that constitutes approximately 21% of Earth’s atmosphere, essential for life and combustion processes, and used in various industrial applications, such as steel production and welding.

Oxygen: A chemical element with symbol “O” and atomic number 8, essential for respiration and combustion.

Oxygenator: A device used in chemical processes or biological systems, such as bioreactors, to enhance the availability of oxygen for the growth of aerobic organisms or to promote the rate of oxidation reactions.

Ozone (O3): An allotrope of oxygen, consisting of three oxygen atoms covalently bonded, with a distinctly pungent odor and strong oxidizing properties. Found in the Earth’s stratosphere, it protects against UV radiation, but ground-level ozone is a major air pollutant.

Ozone Layer: A region of Earth’s stratosphere containing a high concentration of ozone (O3), protecting the planet from harmful ultraviolet radiation.

Ozone: A triatomic form of oxygen (O3) present in Earth’s atmosphere, important for absorbing ultraviolet radiation and protecting life on Earth.

Palladium (Pd): A transition metal with the symbol Pd and atomic number 46, widely used as a catalyst in various chemical reactions, particularly in homogeneous and heterogeneous catalysis, as well as in the electronics industry for its electrical conductivity and resistance to oxidation.

Palladium Catalyst: A catalyst containing palladium, used in various chemical reactions, such as cross-coupling reactions (e.g., Suzuki-Miyaura, Heck, and Stille couplings) to facilitate the formation of new carbon-carbon bonds.

Pancreatic Enzymes: A group of enzymes produced by the pancreas, including amylase, lipase, and protease, which aid in the digestion of carbohydrates, fats, and proteins, respectively, by breaking down complex molecules into simpler components.

Paraffin: A hydrocarbon compound with the general formula CnH2n+2, characterized by single covalent bonds between carbon atoms (alkanes), and typically found in petroleum or as a solid wax at room temperature.

Paramagnetic: A property of substances with unpaired electrons, which are attracted by an external magnetic field.

Partial Pressure: The pressure exerted by an individual gas component within a mixture of gases, equal to the product of the mole fraction of the gas and the total pressure exerted by the entire mixture.

Partial Pressure: The pressure exerted by an individual gas component in a mixture, calculated as its fraction of the total pressure.

Pauli Exclusion Principle: A fundamental principle of quantum mechanics stating that no two electrons in an atom can have the same set of quantum numbers, leading to the formation of electron shells with a maximum of two electrons per energy level.

Pauli Exclusion Principle: A principle stating that no two electrons in an atom can have the same set of quantum numbers.

p-Block Elements: Elements in groups 13 to 18 of the periodic table, characterized by the filling of p orbitals in their valence shells.

Pentane: A straight-chain alkane with five carbon atoms, commonly used as a laboratory solvent.

Peptide Bond: A covalent bond formed between the amino group of one amino acid and the carboxyl group of another, linking amino acid residues in proteins.

Peptide Bond: A covalent bond formed between the carboxyl group of one amino acid and the amino group of another, linking amino acid residues in proteins.

Peptide: A short chain of amino acids linked by peptide bonds, forming the building blocks of proteins and other biomolecules, with various biological functions and roles in cellular processes.

Percent Yield: The ratio of the actual amount of product obtained in a chemical reaction to the theoretical maximum amount that could be produced, expressed as a percentage, indicating the efficiency of the reaction and the presence of side reactions or losses.

Pericyclic Reaction: A type of organic reaction characterized by concerted bond-breaking and bond-forming processes involving cyclic movement of electrons.

Periodate: A chemical compound containing the IO₄⁻ ion, commonly used as an oxidizing agent in organic synthesis.

Periodic Law: The principle stating that the physical and chemical properties of elements are periodic functions of their atomic numbers.

Periodic Table: A tabular arrangement of chemical elements organized by atomic number, electron configuration, and chemical properties.

Periodicity: The repeating pattern of chemical and physical properties of elements across rows and columns of the periodic table.

Permeability: The ability of a substance to pass through a membrane or other barrier, often quantified as the rate of diffusion or the ease with which molecules or ions can cross the barrier.

Peroxide: A compound containing the O₂²⁻ ion or the O-O single bond, often used as a bleaching agent or oxidizing agent.

pH: A measure of the acidity or alkalinity of a solution, defined as the negative logarithm of the hydrogen ion concentration.

Phase Diagram: A graphical representation showing the relationships between temperature, pressure, and phase changes of a substance.

Phase Transition: The change of a substance from one physical state to another, such as melting, freezing, vaporization, or condensation.

Photochemical Reaction: A chemical reaction initiated by the absorption of light energy, leading to the formation of reactive intermediates.

Photoelectron Spectroscopy: A technique used to measure the energy distribution of electrons emitted from a sample after absorption of photons.

Polar Bond: A covalent bond in which electrons are unequally shared between two atoms, creating partial positive and negative charges.

Polar Solvent: A solvent with a partial positive and partial negative charge distribution, capable of dissolving polar and ionic solutes.

Polarimeter: An instrument used to measure the rotation of polarized light caused by chiral substances.

Polarizability: The ability of an atom or molecule to undergo deformation of its electron cloud in the presence of an external electric field.

Polarizability: The ability of an atom or molecule to undergo distortion of its electron cloud in response to an external electric field.

Polarizability: The ability of an atom or molecule to undergo distortion of its electron cloud in response to an external electric field.

Polyatomic Ion: An ion composed of two or more atoms covalently bonded together and carrying a net electrical charge.

Polymer: A large molecule composed of repeating structural units (monomers) linked together by covalent bonds.

Polymerase Chain Reaction (PCR): A laboratory technique used to amplify specific DNA sequences through repeated cycles of DNA denaturation, annealing, and extension.

Polymerization: The process of combining monomer units to form a polymer chain through covalent bonding.

Polymerization: The process of forming a polymer by chemically linking monomer units together to form long chains or networks.

Polyprotic Acid: An acid that can donate more than one proton per molecule in acid-base reactions.

Precipitate: A solid formed from a chemical reaction in a solution, typically insoluble and separating from the liquid phase.

Proteins: Large biomolecules composed of amino acid residues linked by peptide bonds, performing various structural and functional roles in living organisms.

Proteomics: The study of the structure, function, and interactions of proteins in a biological system.

Protic Solvent: A solvent capable of donating hydrogen ions (protons), such as water or alcohols.

Protic Solvent: A solvent capable of donating hydrogen ions (protons), such as water or alcohols.

Proton: A positively charged subatomic particle found in the nucleus of an atom, with a relative charge of +1.

Protonation: The addition of a proton (H⁺ ion) to a molecule, forming a positively charged species called a protonated molecule.

Protonation: The addition of a proton (H⁺ ion) to a molecule, resulting in the formation of a positively charged species.

Pyrimidine: A six-membered heterocyclic aromatic compound containing two nitrogen atoms in the ring structure, found in nucleic acids.

Pyrophosphate: A chemical compound containing the P₂O₇²⁻ ion, commonly found in biological processes such as DNA replication and energy metabolism.

Quadrupole Moment: A measure of the distribution of charge or mass within a molecule or nucleus, leading to an electric or magnetic quadrupole moment.

Quality Control: The process of ensuring that products meet specified standards and requirements through testing and analysis.

Quantitative Analysis: Analysis that determines the quantity or concentration of a substance in a sample using methods like titration, spectrophotometry, or chromatography.

Quantitative Analysis: The determination of the amount or concentration of a substance in a sample using analytical techniques.

Quantum Chemistry: A sub-discipline of chemistry that applies the principles of quantum mechanics to study the electronic structure, molecular properties, and chemical reactivity of atoms, molecules, and extended systems, using computational methods and theoretical models.

Quantum Chemistry: The branch of chemistry that applies quantum mechanics to understand the behavior of atoms and molecules.

Quantum Dot Solar Cell: A type of solar cell that utilizes quantum dots to capture and convert sunlight into electricity.

Quantum Dot: Nanoscale semiconductor particles with unique optical and electronic properties, often used in biological imaging and photovoltaic devices.

Quantum Dots: Nanoscale semiconductor particles with unique optical and electronic properties, used in applications such as biological labeling, imaging, and displays.

Quantum Dots: Semiconductor nanocrystals with unique optical, electronic, and catalytic properties, resulting from quantum confinement effects, used in various applications such as solar cells, LEDs, and biological imaging.

Quantum Entanglement: A phenomenon in quantum mechanics where the states of two or more particles become correlated in such a way that the state of one particle cannot be described independently of the others.

Quantum Mechanics: A branch of physics that describes the behavior of matter and energy at the atomic and subatomic levels.

Quantum Numbers: Numbers that describe the properties of electrons in an atom, including principal, azimuthal, magnetic, and spin quantum numbers.

Quantum Theory: A theoretical framework that describes the behavior of particles and waves on the atomic and subatomic scale.

Quantum Tunneling: A quantum mechanical phenomenon where particles penetrate through potential energy barriers that would be classically impossible to overcome.

Quantum Yield: The efficiency of a process in quantum mechanics, typically referring to the ratio of the number of desired outcomes to the number of possible outcomes.

Quark: Elementary particles that combine to form protons, neutrons, and other hadrons, governed by the strong force.

Quartz Crystal Microbalance: A device used to measure small changes in mass by detecting the frequency shifts of a quartz crystal caused by surface adsorption or desorption.

Quartz: A mineral composed of silicon and oxygen atoms (SiO2) in a tetrahedral crystalline structure, the second most abundant mineral in Earth’s crust and widely used in various industries, including electronics, glassmaking, and as a catalyst support.

Quartz: A mineral composed of silicon dioxide (SiO2), commonly found in rocks and used in various industrial applications.

Quasicrystal: A crystalline material with ordered patterns that do not repeat periodically in space, possessing symmetries forbidden in conventional crystals.

Quasicrystal: A type of crystalline material with long-range order but nonperiodic atomic arrangement.

Quasi-equilibrium: A state in which a reaction appears to be in equilibrium but is actually proceeding slowly in one direction.

Quasiparticle: A collective excitation or state in a solid-state system that behaves like a particle, such as phonons or excitons.

Quaternary Ammonium Compound: A class of organic compounds containing a nitrogen atom bonded to four alkyl or aryl groups, commonly used as disinfectants and surfactants.

Quaternary Ammonium Compound: A type of organic compound containing a positively charged nitrogen atom bonded to four alkyl or aryl groups, often used as surfactants and disinfectants.

Quaternary Ammonium Compound: An organic compound containing an nitrogen atom bound to four alkyl or aryl groups, used as surfactants, disinfectants, and in the synthesis of ion-exchange resins and other functional materials.

Quaternary Carbon: A carbon atom bonded to four other carbon atoms, often found in complex organic molecules.

Quaternary Structure: The arrangement of multiple polypeptide chains (subunits) within a protein or enzyme, folded together in a specific three-dimensional conformation, essential for the protein’s biological function and stability.

Quaternary Structure: The arrangement of multiple polypeptide chains or protein subunits in a protein’s three-dimensional structure.

Quaternary Structure: The highest level of protein structure, referring to the arrangement of multiple protein subunits into a functional complex.

Quaternion: In algebra, a system of four imaginary units (i, j, k) that can be used to represent complex numbers or rotations in three-dimensional space, with applications in quantum mechanics, crystallography, and computer graphics.

Quenched Steel: Steel that has been rapidly cooled from a high temperature to produce specific properties, such as hardness and toughness.

Quencher: A substance added to a solution to decrease the fluorescence intensity of a fluorophore by nonradiative energy transfer.

Quenching Agent: A substance used to rapidly terminate a chemical reaction, luminescence, or excited state by absorbing excess energy, often employed in analytical techniques like fluorescence spectroscopy or to control side reactions

Quenching: In chemistry, the rapid termination of an excited state or reaction, often by the addition of a quencher molecule that absorbs the excess energy and returns the system to its ground state, preventing unwanted side reactions or luminescence.

Quenching: The process of rapidly cooling a hot metal to alter its microstructure and properties.

Quenching: The process of rapidly cooling a hot metal to alter its microstructure and properties.

Quenching: The process of rapidly cooling a hot metal to alter its microstructure and properties.

Quenching: The rapid cooling of a material, such as a metal alloy, to control its properties, often used in metallurgy and heat treatment.

Quinhydrone: A chemical compound formed by the reaction between quinone and hydroquinone, used as a redox indicator.

Quinoid: A molecular arrangement resembling a quinone, characterized by alternating single and double bonds.

Quinoline: A heterocyclic aromatic compound composed of a benzene ring fused to a pyridine ring, commonly found in pharmaceuticals and organic synthesis.

Quinoline: A heterocyclic aromatic compound containing a benzene ring fused to a pyridine ring, commonly found in natural products and pharmaceuticals.

Quinoline: A heterocyclic aromatic compound containing a benzene ring fused to a pyridine ring, commonly found in natural products and pharmaceuticals.

Quinone: A class of organic compounds characterized by a six-membered aromatic ring with two ketone functional groups.

Quinone: A class of organic compounds containing a benzene ring with two ketone groups (carbonyl functionalities) adjacent to each other, exhibiting strong oxidizing properties and found in nature as components of the electron transport chain in mitochondria.

Quinone: A class of organic compounds containing a conjugated cyclic diketone structure, often involved in electron transfer reactions.

Quorum Sensing: A process by which bacteria communicate and coordinate gene expression in response to cell density using signaling molecules.

Radical Polymerization: A polymerization mechanism involving the initiation, propagation, and termination of chain-growth polymerization mediated by free radicals.

Radical Polymerization: A polymerization process initiated by radicals, leading to the formation of polymers with unsaturated bonds.

Radical Substitution: A type of organic reaction in which a hydrogen atom on an alkane is replaced by a halogen atom.

Radical Substitution: A type of organic reaction in which a hydrogen atom on an alkane is replaced by a radical, forming a new carbon-radical bond.

Radical: A species with one or more unpaired electrons, making it highly reactive.

Raman Spectroscopy: A spectroscopic technique based on the inelastic scattering of photons by molecules, providing information about molecular vibrations.

Rancidity: The development of off-flavors and odors in fats and oils due to oxidation or hydrolysis.

Rancidity: The development of unpleasant odors and flavors in fats and oils due to oxidation or hydrolysis.

Rate Constant: The proportionality constant in the rate equation of a chemical reaction, indicating the rate of reaction at a specific temperature.

Rate Law: An equation that describes the relationship between the rate of a chemical reaction and the concentrations of reactants.

Rate Law: An equation that relates the rate of a chemical reaction to the concentrations of reactants.

Rate-Determining Step: The slowest step in a reaction mechanism that determines the overall rate of the reaction.

Rate-Determining Step: The slowest step in a reaction mechanism that limits the overall rate of the reaction.

Rate-Determining Step: The slowest step in a reaction mechanism, determining the overall rate of the reaction.

Rayleigh Scattering: The scattering of light by particles smaller than the wavelength of light, causing the sky to appear blue.

Reaction Coordinate: A measure of the progress of a chemical reaction from reactants to products, often represented graphically.

Reaction Coordinate: A measure of the progress of a chemical reaction from reactants to products, often represented graphically.

Reaction Coordinate: A representation of the progress of a chemical reaction from reactants to products, often shown graphically.

Reaction Mechanism: The series of elementary steps by which a chemical reaction occurs, including the formation and breaking of chemical bonds.

Reaction Mechanism: The step-by-step sequence of elementary reactions by which a chemical reaction occurs, including bond-breaking and bond-forming steps.

Reaction Rate: The speed at which a chemical reaction occurs, measured by the change in concentration of reactants or products over time.

Reaction Yield: The amount of product obtained in a chemical reaction compared to the theoretical maximum amount that could be obtained.

Reaction Yield: The amount of product obtained in a chemical reaction compared to the theoretical maximum amount that could be obtained.

Reactive Intermediates: Short-lived species formed in chemical reactions that are neither reactants nor products but play crucial roles in reaction mechanisms.

Reactivity Series: A list of metals arranged in order of their reactivity, with more reactive metals displacing less reactive metals from their compounds.

Reactivity Series: A list of metals ranked in order of their reactivity, often used to predict displacement reactions in aqueous solutions.

Reactivity: The tendency of a substance to undergo chemical reactions based on its chemical structure.

Reagent: A substance or compound used in a chemical reaction to bring about a specific transformation.

Reagent: A substance or compound used to bring about a chemical reaction, often added to a reaction mixture to produce a desired transformation.

Reagent: A substance used in a chemical reaction to bring about a specific transformation.

Redox Reaction: A chemical reaction involving the transfer of electrons between reactants, resulting in changes in oxidation states.

Redox Titration: A titration method based on a redox reaction between the analyte and a titrant, often using a redox indicator.

Reducing Agent: A substance that donates electrons to another substance, causing it to be reduced.

Reducing Agent: A substance that donates electrons, causing another substance to be reduced in a redox reaction.

Reduction: The gain of electrons by a chemical species, resulting in a decrease in oxidation state.

Reflux: A laboratory technique involving continuous boiling and condensation of a reaction mixture to ensure thorough mixing and completion of a reaction.

Reflux: A technique in organic chemistry involving continuous boiling and condensation of a reaction mixture to ensure completion of a reaction.

Reflux: A technique in organic chemistry where a reaction mixture is heated to boiling and the vapors are condensed and returned to the reaction vessel.

Refractive Index: A measure of how much light bends as it passes through a substance, related to its composition and density.

Refractive Index: A measure of how much light bends as it passes through a substance, indicating the speed of light in that medium relative to vacuum.

Refrigerant: A substance used in refrigeration systems to transfer heat from one location to another.

Refrigerant: A substance used in refrigeration systems to transfer heat from one location to another.

Regioselectivity: The preference of a reaction to occur at one site on a molecule over another, leading to the formation of specific regioisomers.

Regioselectivity: The preference of a reaction to occur at one site on a molecule over others, leading to the formation of specific regioisomers.

Residue: The portion of a compound or substance that remains after a process, such as evaporation or combustion.

Residue: The portion of a compound or substance that remains after a process such as purification or combustion.

Residue: The remaining substance after a chemical reaction or physical process.

Resonance Energy: The stabilization energy associated with resonance structures, reflecting the delocalization of electrons in a molecule.

Resonance Energy: The stabilization energy associated with resonance structures, representing the energy difference between the real molecule and its most stable contributing resonance structure.

Resonance Hybrid: A molecular structure that is a combination of two or more resonance structures, reflecting the delocalization of electrons.

Resonance Structure: One of multiple Lewis structures that can be drawn for a molecule or ion to represent its electronic configuration.

Resonance: The delocalization of electrons in molecules or ions, represented by different Lewis structures.

Ring Strain: The strain energy associated with non-ideal bond angles or torsional strain in cyclic molecules.

Ring Strain: The strain or instability in cyclic compounds due to unfavorable bond angles or torsional strain.

RNA: Ribonucleic acid, a nucleic acid molecule essential for various biological functions, including protein synthesis.

RNA: Ribonucleic acid, a nucleic acid molecule essential for various biological functions, including protein synthesis.

Rotational Energy: The kinetic energy associated with the rotation of molecules about their center of mass.

Rotational Energy: The kinetic energy associated with the rotation of molecules around their center of mass.

Ruthenium: A transition metal element with the atomic number 44 and symbol Ru, used in catalysts and as a coating for electrical contacts.

Ruthenium: A transition metal element with the symbol Ru and atomic number 44, used in catalysts and electrical contacts.

Salt Bridge: A conductive pathway used in electrochemical cells to maintain electrical neutrality by allowing the flow of ions between half-cells.

Salt: An ionic compound formed by the reaction of an acid with a base, consisting of positive and negative ions.

Saponification: A chemical reaction in which a fat or oil reacts with a strong base (usually an alkali) to produce soap and glycerol, involving the hydrolysis of ester bonds in the fatty acid chains.

Saponification: The hydrolysis of ester bonds in fats and oils by reaction with a strong base, yielding soap and glycerol.

Scanning Electron Microscope (SEM): An advanced microscopy technique that uses a focused electron beam to scan and image the surface of a sample, providing high-resolution images with topographical and compositional information, particularly useful for studying materials, minerals, and biological specimens.

Schottky Defect: In solid-state chemistry, a type of defect in a crystal lattice where a cation and anion vacancy occur together, disrupting the regular arrangement of ions in the crystal structure and affecting its electrical and optical properties.

Scintillation Counter: An instrument used to detect and measure ionizing radiation, such as alpha particles, beta particles, and gamma rays, by converting the radiation into flashes of light (scintillations) in a scintillator material, which are then counted by a photomultiplier tube.

Secondary Cell: A type of rechargeable battery, such as a nickel-cadmium (NiCd), nickel-metal hydride (NiMH), or lithium-ion (Li-ion) battery, capable of being discharged and recharged multiple times due to the reversible electrochemical reactions occurring between the active materials in the cell.

Secondary Structure: In the study of proteins, the local folding pattern of the polypeptide chain, primarily involving hydrogen bonding between the backbone amide and carbonyl groups, resulting in regularly repeating patterns like alpha-helices and beta-sheets, which contribute to the overall tertiary structure.

Sedimentation: The process of particles settling under the influence of gravity or other forces in a fluid, driven by differences in density, size, or shape between the particles and the surrounding medium, leading to the deposition of sediments in a new location.

Selective Permeability: The property of a membrane that allows certain substances to pass through while restricting the passage of others.

Selectivity: In chemistry, the ability of a chemical reaction, catalyst, or separation technique to preferentially favor one reactant, product, or component over another, based on differences in their physical or chemical properties, such as size, polarity, or charge.

Self-Assembly: A process in which complex structures or patterns emerge from the spontaneous organization of simpler components, driven by non-covalent interactions like hydrogen bonding, van der Waals forces, or electrostatic interactions, often observed in supramolecular chemistry and biological systems.

Semiconductor: A material with electrical conductivity between that of a conductor and an insulator, whose conductivity can be controlled by temperature or impurities.

Semiconductor: A material with electrical conductivity between that of a conductor and an insulator, exhibiting a partial transfer of electrons in its crystal lattice, which can be manipulated by applying an external electric field or by doping with impurities, used in various electronic devices and solar cells.

Shell: A group of atomic orbitals with similar energy levels, designated by the principal quantum number (n), and containing electrons with similar properties.

Sigma Bond: A covalent bond formed by the head-on overlap of atomic orbitals along the internuclear axis.

Sigma Bond: A covalent bond formed by the overlap of atomic orbitals along the axis connecting the nuclei of the bonded atoms.

Single Displacement Reaction: A chemical reaction in which one element replaces another element in a compound, typically with the more reactive element displacing the less reactive one.

Solubility Product Constant: The equilibrium constant for the dissolution of a sparingly soluble salt in water.

Solubility Product: The equilibrium constant for the dissolution of a sparingly soluble compound in water, representing the product of the concentrations of its ions.

Solubility: The ability of a substance to dissolve in a solvent at a specific temperature and pressure.

Solute: A substance that is dissolved in a solvent to form a solution.

Solution: A homogeneous mixture composed of two or more substances uniformly dispersed at the molecular level.

Solvent: A substance capable of dissolving other substances, forming a homogeneous mixture called a solution.

Specific Heat Capacity: The amount of heat energy required to raise the temperature of one gram of a substance by one degree Celsius.

Spectator Ion: An ion present in a solution that does not participate in a chemical reaction or undergo any change in oxidation state.

Spectrophotometry: A technique used to measure the concentration of a substance in a solution by analyzing its absorption or emission of light at specific wavelengths.

Spectroscopy: The study of the interaction between electromagnetic radiation and matter, used to analyze the structure and composition of substances.

Spectroscopy: The study of the interaction between electromagnetic radiation and matter, used to determine the structure, composition, and properties of substances.

Spin: A fundamental property of particles, such as electrons, characterized by angular momentum and associated with magnetic behavior.

Spontaneous Reaction: A chemical reaction that occurs without external intervention, driven by a negative change in Gibbs free energy.

Spontaneous Reaction: A reaction that occurs naturally without external intervention, typically characterized by a negative change in Gibbs free energy.

Standard Electrode Potential: The potential difference between a half-reaction and the standard hydrogen electrode, used to predict the direction of redox reactions.

Standard Solution: A solution of known concentration used in chemical analysis and titration experiments to determine the concentration of other solutions.

Standard Temperature and Pressure (STP): The conditions of 0 degrees Celsius and 1 atmosphere pressure used as a reference in gas calculations.

Stereochemistry: The study of the spatial arrangement of atoms within molecules and the effect of this arrangement on chemical properties.

Stereoisomer: Molecules with the same molecular formula and connectivity of atoms but differing in spatial arrangement of atoms.

Steric Hindrance: The interference or blocking of chemical reactions due to the bulky size of substituents or groups on a molecule.

Stoichiometric: Having a balanced ratio of reactants in a chemical reaction, such that all reactants are consumed and no excess remains.

Stoichiometry: The quantitative relationship between the amounts of reactants and products in a chemical reaction.

Strong Acid: An acid that completely dissociates into ions when dissolved in water, resulting in a high concentration of hydronium ions.

Strong Base: A base that completely dissociates into ions when dissolved in water, resulting in a high concentration of hydroxide ions.

Structural Isomer: Compounds with the same molecular formula but different structural arrangements of atoms.

Sublimation: The process by which a substance transitions directly from a solid to a gas phase without passing through the liquid phase.

Substrate: A reactant molecule that undergoes a chemical reaction catalyzed by an enzyme or other catalyst.

Supersaturated Solution: A solution that contains more solute than would normally dissolve at a given temperature, usually formed by cooling a heated saturated solution.

Surface Area: The total area of the exposed surface of a solid object, often influencing the rate of chemical reactions occurring at the surface.

Surface Tension: The force per unit length acting perpendicular to the surface of a liquid, caused by the attraction between liquid molecules.

Synthesis Reaction: A chemical reaction in which two or more substances combine to form a single, more complex product.

Tautomer: Isomers that can interconvert rapidly via a proton transfer, often differing in the position of a hydrogen atom and a double bond.

Tautomerism: An interconversion between two structurally different forms of a molecule (tautomers) within the same chemical species, involving the migration of a proton (hydrogen atom) and a change in the functional groups’ connectivity, commonly observed in compounds containing hydrogen bond donors and acceptors.

Tautomerism: Isomerism involving the rapid interconversion of constitutional isomers through proton transfer.

Tautomerization: The process of isomerization between tautomers, which are constitutional isomers that differ in the placement of a hydrogen atom and a double bond.

Temperature: A measure of the average kinetic energy of particles in a substance.

Terminal Alkyne: A hydrocarbon compound containing a carbon-carbon triple bond at the end of the carbon chain.

Ternary Acid: An acid composed of three elements: hydrogen, oxygen, and another element (typically a nonmetal).

Ternary Compound: A compound composed of three different elements.

Ternary System: A system consisting of three components, such as a mixture of three substances or a chemical compound containing three elements.

Terpene: A class of hydrocarbon compounds synthesized by plants and fungi, often serving as precursors to steroids, vitamins, and other organic molecules.

Tetrahedral Geometry: A molecular geometry in which a central atom is bonded to four other atoms, arranged symmetrically around a central point.

Tetrahedral: A molecular geometry in which a central atom is surrounded by four bonded atoms, forming a shape resembling a tetrahedron.

Theoretical Yield: The maximum amount of product that could be obtained in a chemical reaction based on stoichiometry.

Therapeutic Index: The ratio of the dose of a drug that produces toxicity to the dose that produces a therapeutic effect, used to assess the safety and efficacy of pharmaceuticals.

Thermal Conductivity: The ability of a material to conduct heat, measured in watts per meter per Kelvin (W/(m·K)).

Thermochemistry: The branch of chemistry concerned with the study of heat changes in chemical reactions.

Thermocouple: A temperature-sensing device consisting of two different metals joined at one end, generating a voltage proportional to the temperature difference between the junctions.

Thermodynamics: A branch of chemistry and physics that deals with the study of energy transformations and the factors affecting them, particularly in terms of heat, work, and temperature, focusing on the principles of equilibrium, efficiency, and spontaneity in chemical and physical processes.

Thermodynamics: The branch of physical science that deals with the relationships between heat, work, and energy, as well as the properties of systems in equilibrium and non-equilibrium states.

Thermodynamics: The branch of physics and chemistry that deals with energy and heat transfer during chemical reactions and physical changes.

Thermogravimetric Analysis (TGA): A technique used to study the decomposition of materials as a function of temperature, by measuring changes in mass.

Thermogravimetric Analysis (TGA): An analytical technique that measures the change in mass of a sample as a function of temperature or time under a controlled atmosphere, providing information about the thermal stability, composition, and decomposition processes of materials, particularly useful for polymers, ceramics, and composites.

Thermoplastic: A polymer that softens when heated and solidifies upon cooling, allowing it to be molded into different shapes.

Thiol: An organic compound containing a sulfhydryl group (-SH), analogous to an alcohol but with sulfur replacing oxygen.

Thixotropy: A property exhibited by certain gels, pastes, or suspensions that experience a decrease in viscosity when subjected to mechanical stress or shear, returning to their original viscosity upon rest or cessation of stress, useful in paints, cosmetics, and other applications.

Thixotropy: The property of certain gels or fluids to become less viscous under shear stress and return to a higher viscosity when the stress is removed.

Threshold Energy: The minimum energy required for a chemical reaction to occur, often related to the activation energy.

Titration Curve: A plot of pH (or other property) versus the volume of added titrant during a titration, used to determine equivalence points and pKa values.

Titration: A laboratory technique used to determine the concentration or amount of a substance in a solution by reacting it with a known concentration of a titrant (reagent) until a specific endpoint is reached, often indicated by a color change, pH shift, or other detectable signal.

Titration: A technique used to determine the concentration of a solution by reacting it with a solution of known concentration.

Total Internal Reflection: The phenomenon in which light traveling within a medium strikes the boundary with another medium at an angle greater than the critical angle, resulting in reflection back into the original medium.

Total Synthesis: The complete chemical synthesis of a complex organic molecule from simpler starting materials.

Toxicity: The degree to which a substance can harm living organisms, typically measured by its dose-response relationship.

Trace Element: An element present in minute quantities in a substance or organism but essential for its proper functioning.

Transcription Factor: A protein that binds to specific DNA sequences, regulating the transcription of genetic information from DNA to RNA.

Transcription: The process by which an RNA molecule is synthesized from a DNA template, catalyzed by RNA polymerase.

Transition Metal Complex: A compound containing a central transition metal ion coordinated to one or more ligands through coordinate covalent bonds.

Transition Metal: A metal from the d-block of the periodic table that can adopt different oxidation states and coordination geometries, forming a wide range of coordination compounds and exhibiting variable magnetic and electronic properties, essential in catalysis, coordination chemistry, and materials science.

Transition Metal: An element located in the d-block of the periodic table, characterized by the presence of incompletely filled d orbitals in its atomic structure.

Transition State Theory: A theory that describes the rate of a chemical reaction in terms of the formation and stabilization of a transition state.

Transition State: A high-energy, unstable intermediate state formed during a chemical reaction, representing the maximum energy point along the reaction pathway.

Transition State: In chemical kinetics, a high-energy, short-lived intermediate formed during the progress of a reaction, representing the highest energy point along the reaction coordinate and the slowest step in the reaction mechanism, often characterized by a unique geometry and bonding situation.

Transmutation: A nuclear process in which an atomic nucleus changes its chemical identity by transforming one element into another, resulting from the conversion of one type of nucleon (proton or neutron) into another, typically induced by bombarding the nucleus with high-energy particles or photons.

Transpiration: The process of water vapor release from plants, primarily through stomata in the leaves, as part of their natural water balance and gas exchange, playing a crucial role in the water cycle and maintaining the Earth’s atmosphere.

Tribology: The scientific study of interacting surfaces in relative motion, including friction, lubrication, wear, and related phenomena, with applications in engineering, materials science, and chemistry, particularly in the development of efficient and durable machines, engines, and coatings.

Triple Bond: A covalent bond formed by the sharing of three pairs of electrons between two atoms.

Triple Point: The temperature and pressure at which the solid, liquid, and gas phases of a substance coexist in equilibrium.

Triplet State: A molecular electronic state with two unpaired electrons of opposite spin, higher in energy than the singlet state.

Trituration: A process of grinding or pulverizing a substance into fine particles, often used in pharmaceutical preparations.

Tyndall Effect: The scattering of light by colloidal particles or large molecules in a solution, making the light path visible.

Ullmann Reaction: A cross-coupling reaction between two aryl halides or related compounds in the presence of a copper catalyst, used in organic synthesis to form biaryls.

Ultracentrifugation: A technique used to separate particles based on their size, shape, and density using high centrifugal forces in an ultracentrifuge.

Ultramicrobalance: An extremely sensitive balance capable of measuring small masses with high precision, often used in analytical chemistry and nanotechnology.

Ultrasonic Cleaning: A method of cleaning objects using ultrasound waves to dislodge and remove contaminants from surfaces.

Ultrasonication: The application of ultrasound waves to a solution or mixture to break down particles, disperse materials, or accelerate chemical reactions.

Ultraviolet (UV) Radiation: Electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays, commonly associated with sunlight and used in various chemical and biological applications.

Ultraviolet (UV) Radiation: Electromagnetic radiation with wavelengths shorter than visible light (between 10 nm and 400 nm) but longer than X-rays, capable of causing photochemical reactions, sunburn, and damage to biological tissues, including DNA, which can lead to skin cancer and other health issues.

Ultraviolet Protection Factor (UPF): A rating system used to indicate the effectiveness of clothing or sunscreen in blocking ultraviolet radiation from the sun.

Ultraviolet-visible (UV-Vis) Spectroscopy: A technique used to analyze the absorption or transmission of ultraviolet and visible light by molecules, providing information about electronic transitions.

Umbrella Effect: A phenomenon in stereochemistry where the presence of bulky substituents near a reaction center affects the stereochemical outcome of a reaction.

Underpotential Deposition: The electrochemical process in which a metal is deposited onto a substrate at a potential less negative than its equilibrium potential.

Underpotential Deposition: The process of depositing a metal onto a substrate at a potential less negative than its equilibrium potential, often used in electrochemistry.

Unified Atomic Mass Unit (u): A unit of mass used to express atomic and molecular masses, defined as one-twelfth the mass of a carbon-12 atom.

Uniformity: The degree to which a substance or mixture is consistent or homogeneous throughout.

Unimolecular Decomposition: A chemical reaction in which a single molecule decomposes to form two or more products.

Unimolecular Reaction: A chemical reaction that involves the decomposition or rearrangement of a single molecule to form one or more products.

Unit Cell: The smallest repeating unit of a crystal lattice in a crystalline solid, representing the geometric arrangement of atoms or ions.

Unitary Reaction: A chemical reaction that occurs in a single step without the formation of intermediate species.

Universal Indicator: A mixture of pH indicators that changes color over a wide pH range, often used to determine the approximate pH of a solution.

Unsaturated Compound: A compound containing carbon-carbon double or triple bonds, allowing for the addition of other atoms or groups.

Unsaturated Fat: A type of fat or lipid containing carbon-carbon double bonds in its hydrocarbon chain, typically liquid at room temperature.

Unsaturated Fat: A type of fat or lipid containing one or more double bonds between carbon atoms in the fatty acid chains, resulting in a kinked or bent structure and lower melting points compared to saturated fats, examples include polyunsaturated and monounsaturated fats.

Unsaturated Fatty Acid: A fatty acid molecule with one or more carbon-carbon double bonds in its hydrocarbon chain, commonly found in vegetable oils and fish.

Unsaturated Hydrocarbon: A hydrocarbon molecule containing one or more carbon-carbon double or triple bonds, capable of undergoing addition reactions.

Unsaturated Polyester Resin: A thermosetting polymer formed by the condensation polymerization of unsaturated dicarboxylic acids with diols, commonly used in fiberglass and composite materials.

Unsaturated Polyester: A type of polymer formed from the condensation polymerization of unsaturated dicarboxylic acids with diols or polyols, commonly used in fiberglass composites and coatings.

Unsaturated Solution: A solution containing less solute than it could dissolve at a given temperature, typically formed when not all of the solute has dissolved.

Unsaturated Solution: A solution in which the solute concentration is less than the maximum amount that could dissolve at a given temperature, leading to the potential for further dissolution.

Unsaturated Solution: A solution that contains less solute than the maximum amount that could dissolve at a given temperature, forming a dynamic equilibrium with undissolved solute.

Unsaturation: The presence of one or more double or triple bonds between carbon atoms in a molecule.

Upconversion: The process by which a material absorbs two or more photons of lower energy and emits a single photon of higher energy.

Upfield: In NMR spectroscopy, the direction of chemical shift towards higher magnetic field strengths, typically observed for shielded nuclei.

Upper Critical Solution Temperature (UCST): The temperature above which a homogeneous solution becomes unstable and phase separates into two immiscible liquid phases.

Uptake Kinetics: The study of the rate at which substances are absorbed by cells or tissues, often influenced by factors such as concentration gradients and membrane transport mechanisms.

Uptake: The process of absorbing or taking in a substance, such as nutrients by cells or gases by porous materials.

Uracil: One of the four nucleobases found in RNA, capable of forming hydrogen bonds with adenine during nucleic acid synthesis.

Uracil-DNA Glycosylase (UDG): An enzyme that catalyzes the removal of uracil bases from DNA molecules, important for DNA repair mechanisms.

Uracil-DNA Glycosylase: An enzyme that catalyzes the removal of uracil bases from DNA molecules by cleaving the N-glycosidic bond between the uracil base and the sugar phosphate backbone.

Uranium Enrichment: The process of increasing the proportion of the fissile isotope uranium-235 in natural uranium, typically for nuclear fuel production.

Uranium: A radioactive metallic element with the atomic number 92 and symbol U, used as fuel in nuclear reactors and for the production of nuclear weapons.

Uranium: A silvery-white, radioactive metal found in trace amounts in the Earth’s crust, with the atomic number 92, used as a fuel in nuclear power plants and as the primary fissile material in nuclear weapons, along with its isotopes U-235 and U-238.

Urea: A nitrogen-containing organic compound with the chemical formula CO(NH2)2, often used as a fertilizer and in the production of plastics and resins.

Urea: A water-soluble organic compound (carbamide) with the chemical formula CO(NH2)2, formed in the body as a waste product from protein metabolism and excreted through urine, also used as a nitrogen-rich fertilizer and a precursor for the production of various chemicals like plastics and resins.

Uronic Acid: A sugar acid derived from the oxidation of the primary alcohol group at the C6 position of a monosaccharide, commonly found in glycosaminoglycans and pectins.

UV-Visible Spectroscopy: An analytical technique that measures the absorption or reflection of ultraviolet and visible light by a sample, providing information about its molecular structure, electronic transitions, and concentration, widely used in chemistry, biochemistry, and materials science.

Vacancy Defect: A type of crystal defect characterized by the absence of an atom from its lattice site in a crystalline solid.

Vacuum: A space devoid of matter or containing significantly lower pressure than atmospheric pressure.

Valence Electron: An electron in the outermost shell of an atom, responsible for the atom’s chemical properties and bonding behavior.

Valency: The combining power of an element, determined by the number of electrons it can gain, lose, or share to form chemical bonds.

Valine: An essential amino acid with the chemical formula CH3(CH2)3CH(NH2)COOH, important for protein synthesis and metabolism.

Van der Waals Forces: Weak attractive or repulsive forces between molecules or atoms, including dispersion forces, dipole-dipole interactions, and hydrogen bonding.

Van der Waals Forces: Weak, non-covalent interactions between atoms or molecules, resulting from temporary fluctuations in electron distribution, leading to instantaneous dipoles and transient attractions, playing a crucial role in molecular recognition, self-assembly, and supramolecular chemistry.

Vanadium Pentoxide: A chemical compound with the formula V2O5, used as a catalyst in various oxidation reactions and as a pigment in ceramics.

Vanadium Redox Flow Battery: A type of rechargeable battery that stores energy by employing vanadium ions in different oxidation states to store and release electrical energy.

Vanadium: A transition metal element with the symbol V and atomic number 23, used in alloys and as a catalyst.

Vanillin: A compound that imparts the characteristic flavor and aroma of vanilla, often synthesized from lignin or extracted from vanilla beans.

Vapochromism: The phenomenon in which the color of a compound changes upon exposure to different vapor species, often due to structural changes in the molecule.

Vapor Pressure: The pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature, dependent on the strength of the intermolecular forces and the volatility of the substance, used in thermodynamics, phase diagrams, and the design of chemical reactors and distillation columns.

Vapor Pressure: The pressure exerted by a vapor in equilibrium with its liquid or solid phase at a given temperature.

Vapor Pressure: The pressure exerted by a vapor in equilibrium with its condensed phase (liquid or solid) at a given temperature.

Vaporization: The process by which a liquid changes into a vapor or gas phase, typically occurring at the boiling point.

Vapor-Liquid Equilibrium: The equilibrium established between the vapor phase and the liquid phase of a substance in a closed system at a specific temperature and pressure.

Vapor-Liquid-Solid (VLS) Mechanism: A process in the synthesis of nanomaterials, particularly semiconductor nanowires, where a metal catalyst particle (liquid) is suspended in a vapor-phase precursor, leading to the nucleation and growth of the nanowire on the catalyst surface, guided by the surface tension and diffusion of the species involved.

Vaterite: A crystalline form of calcium carbonate with the mineralogical formula CaCO3, found in certain geological formations and as a precursor to other calcium carbonate polymorphs.

Vermiculite: A group of hydrated laminar minerals with a high cation exchange capacity, often used in soil conditioning and as a component of fire-resistant materials.

Vesicle: A small, membrane-bound sac filled with fluid or cellular material, involved in transport and storage within cells.

Vibrational Energy: The energy associated with the motion of atoms within a molecule as they vibrate around their equilibrium positions.

Vibrational Spectroscopy: Techniques used to study molecular vibrations by measuring the absorption, emission, or scattering of electromagnetic radiation.

Vibronic Transition: A type of electronic transition in molecules that involves both changes in electronic energy levels and vibrational energy levels.

Vinyl Chloride: A colorless gas with the formula CH2=CHCl, used primarily in the production of polyvinyl chloride (PVC) plastic.

Vinylation: The introduction of a vinyl group (-CH=CH2) into a molecule, often used in organic synthesis to form carbon-carbon double bonds.

Vinylation: The process of introducing a vinyl group (-CH=CH2) into a molecule, often used in organic synthesis to form carbon-carbon double bonds.

Viscoelasticity: The combined properties of viscosity (resistance to flow) and elasticity (ability to return to original shape), observed in certain materials like polymers and gels.

Viscosity: A measure of a fluid’s resistance to flow, influenced by intermolecular forces and temperature.

Vitamin C: A water-soluble vitamin with the chemical formula C6H8O6, also known as ascorbic acid, important for collagen synthesis and antioxidant functions.

Vitamin: A micronutrient essential for the normal functioning of metabolic processes and physiological functions in organisms.

Vitriol: An archaic term for sulfuric acid (H2SO4) or any sulfate salt, historically used in alchemy and chemical processes.

Vogel’s Approximation Method: A technique used to estimate the pH of a solution based on the concentrations of its acidic and basic components.

Volatile Organic Compound (VOC): Organic compounds that easily evaporate into the atmosphere, contributing to air pollution and environmental concerns.

Volatile: A substance that readily evaporates at normal temperatures and pressures, often characterized by high vapor pressure.

Volatility: The tendency of a substance to vaporize or evaporate, typically measured by its vapor pressure and boiling point.

Voltammetry: An electrochemical technique used to measure the current as a function of applied voltage, providing information about redox reactions and electrode processes.

Voltammetry: An electrochemical technique used to study the behavior of electroactive species by measuring the current as a function of applied potential.

Volumetric Analysis: A quantitative analytical technique based on measuring the volume of a reactant solution of known concentration required to react completely with another substance.

Vortex: A swirling motion of fluid or gas, often generated by the rotation of an object or by convection currents.

VSEPR Theory: The Valence Shell Electron Pair Repulsion theory, which predicts the molecular geometry of covalent molecules based on the repulsion between electron pairs.

Vulcanization: The chemical process of cross-linking polymer chains in rubber or other elastomers to improve their strength, elasticity, and durability.

Vulcanization: The process of cross-linking polymer chains in rubber or other elastomers to improve their strength, elasticity, and durability.

Waste Management: The process of collecting, transporting, treating, and disposing of waste materials in an environmentally responsible manner.

Waste Minimization: The reduction of waste generation through process optimization, recycling, reuse, and other environmentally friendly practices.

Water Bath: A laboratory apparatus used to heat or cool samples indirectly by immersing them in a container of water at a constant temperature.

Water Hardness: The concentration of dissolved minerals, primarily calcium and magnesium ions, in water, affecting its ability to lather with soap and causing scaling in pipes.

Water of Hydration: Water molecules that are incorporated into the crystalline structure of a compound through hydration.

Water Pollution: Contamination of water bodies, such as rivers, lakes, and oceans, by harmful substances, including chemicals, pathogens, and pollutants.

Water Quality: The physical, chemical, and biological characteristics of water, affecting its suitability for various purposes, including drinking, recreation, and ecosystem health.

Water Softening: The process of removing calcium and magnesium ions from hard water to prevent the buildup of scale in pipes and appliances.

Water Treatment: The process of purifying water to make it safe for consumption or suitable for specific industrial or agricultural uses.

Water: A colorless, odorless, and tasteless liquid compound composed of hydrogen and oxygen (H2O), essential for life and widely used as a solvent, coolant, and reagent in chemical reactions.

Wave Packet: A localized group or bundle of waves with a characteristic frequency spectrum, often used to describe the behavior of particles in quantum mechanics.

Wavefunction: A mathematical function that describes the behavior of a particle or system in quantum mechanics, often representing the probability amplitude of finding a particle at a given position and time.

Wavelength Dispersive X-ray Spectroscopy (WDS): An analytical technique used to determine the elemental composition of a sample by measuring the characteristic X-rays emitted upon irradiation with high-energy electrons.

Wavelength: The distance between successive crests or troughs of a wave, such as electromagnetic radiation or sound waves, measured in meters.

Wavelength: The distance between two consecutive peaks or troughs of a wave, such as electromagnetic radiation or sound waves.

Weak Acid: A substance that partially dissociates into ions in solution, resulting in a low concentration of hydronium ions (H₃O⁺).

Weak Acid: An acid that only partially dissociates in solution, resulting in a lower concentration of hydronium ions compared to strong acids.

Weak Base: A base that only partially dissociates in solution, resulting in a lower concentration of hydroxide ions compared to strong bases.

Weak Base: A compound that accepts protons (H⁺ ions) to a limited extent in aqueous solution, resulting in a lower concentration of hydroxide ions (OH⁻).

Weakly Acidic: Refers to a substance that exhibits weak acidic properties, characterized by a low degree of ionization in aqueous solution.

Werner Complex: A coordination complex proposed by Alfred Werner, consisting of a central metal ion surrounded by ligands in fixed positions.

Wet Chemistry: Traditional laboratory techniques that involve the use of liquids, such as solvents and reagents, to perform chemical reactions and analyses.

Wheatstone Bridge: An electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit.

Wheatstone Bridge: An electrical circuit used to measure an unknown electrical resistance by comparing it with known resistances in a balanced configuration.

White Phosphorus: A highly reactive, translucent, waxy solid form of the element phosphorus, consisting of P4 molecules, which ignites spontaneously in air.

Wilson Cloud Chamber: A device used to visualize the tracks of charged particles, such as alpha and beta particles, by condensation trails in supersaturated vapor.

Wittig Reaction: A chemical reaction that converts a carbonyl compound into an alkene using a phosphonium ylide and a base.

Woodward-Hoffmann Rules: A set of rules in organic chemistry used to predict the stereochemical outcome of pericyclic reactions based on orbital symmetry considerations.

Woodward-Hoffmann Rules: A set of rules used to predict the stereochemical outcome of pericyclic reactions based on orbital symmetry considerations.

Work Function: The minimum energy required to remove an electron from the surface of a material, typically measured in electron volts (eV).

Work Function: The minimum energy required to remove an electron from the surface of a material, typically measured in electron volts (eV).

Wulff Construction: A geometric method used to determine the equilibrium shape of a crystal based on its surface energy and crystallographic orientation.

Wulff Construction: A graphical method used to determine the equilibrium shape of a crystal based on its surface energies and crystallographic orientations.

Wulff Net: A graphical method used to determine the orientation of crystal faces on a stereographic projection, aiding in crystallographic analysis.

Wurtz Reaction: A chemical reaction in which two alkyl halides react with metallic sodium to form a higher alkane and sodium halide.

Wurtz Reaction: A chemical reaction in which two alkyl halides react with metallic sodium to form a higher alkane and sodium halide.

Wurtz Reaction: A chemical reaction that converts alkyl halides into alkanes by coupling two molecules of alkyl halides using metallic sodium.

Wurtz Synthesis: A chemical reaction that produces an alkane by coupling two alkyl halides in the presence of sodium metal.

Wurtz-Fittig Reaction: A reaction that combines two different alkyl or aryl halides to form a new carbon-carbon bond using metallic sodium.

Wurtzite Structure: A crystal structure found in certain compounds, characterized by hexagonal close packing of atoms with alternating layers of two different types.

Xanthate: A salt or ester of xanthic acid, commonly used as a flotation agent in mineral processing and as a chemical intermediate in organic synthesis.

Xanthate: A salt or ester of xanthic acid, used as a flotation agent in mineral processing and as a chemical intermediate in organic synthesis.

Xenobiosis: The study of the interactions between organisms and foreign substances or chemicals, such as drugs, pollutants, or environmental toxins.

Xenobiotic: A foreign compound or substance that is not naturally produced or expected to be present in an organism, often referring to drugs, pollutants, or environmental contaminants.

Xenobiotic: A foreign compound or substance that is not naturally produced or expected to be present in an organism, often referring to drugs, pollutants, or environmental contaminants.

Xenodiagnosis: A diagnostic technique in parasitology involving the use of a suitable vector organism to detect the presence of parasites in a host.

Xenolith: A rock fragment or inclusion that is foreign to the surrounding igneous rock, often brought to the surface during volcanic eruptions.

Xenolith: A rock fragment or inclusion that is foreign to the surrounding igneous rock, often brought to the surface during volcanic eruptions.

Xenomorphism: The occurrence of foreign or exotic mineral phases within a rock or geological formation.

Xenon Hexafluoride: A chemical compound with the formula XeF6, used as a powerful oxidizing agent and in the synthesis of other xenon compounds.

Xenon Tetroxide: A chemical compound with the formula XeO4, a strong oxidizing agent used in the synthesis of other xenon compounds.

Xenon: A noble gas element with the atomic number 54 and symbol Xe, commonly used in lighting, anesthesia, and various laser applications.

Xenophile: A molecule or organism that exhibits an affinity or attraction towards foreign substances or molecules.

Xenophile: An organism or molecule that exhibits an affinity or attraction towards foreign substances or molecules.

Xenoproteomics: The study of proteins or proteomes from non-model organisms, often using advanced analytical techniques such as mass spectrometry.

Xeriscaping: Landscaping or gardening practices designed to conserve water and reduce the need for irrigation in arid or drought-prone regions.

Xeriscaping: Landscaping or gardening practices designed to conserve water and reduce the need for irrigation in arid or drought-prone regions.

Xerogel: A porous solid material derived from a gel by removing the liquid phase, often used as a catalyst support or in adsorption applications.

Xerogel: A porous solid material derived from a gel by removing the liquid phase, often used as a catalyst support or in adsorption applications.

Xerophthalmia: A medical condition characterized by dryness of the eyes due to insufficient tear production, often caused by vitamin A deficiency.

Xerophyte: A plant adapted to survive in arid or dry environments, characterized by features such as reduced leaf surface area and water-storing tissues.

Xerophyte: A plant adapted to survive in arid or dry environments, characterized by features such as reduced leaf surface area and water-storing tissues.

Xerothermic Reaction: A chemical reaction that releases heat to the surroundings, often accompanied by an increase in temperature.

Xerothermic Reaction: A chemical reaction that releases heat to the surroundings, often accompanied by an increase in temperature.

X-ray Absorption Fine Structure (XAFS): A spectroscopic technique used to study the local atomic structure of materials by analyzing the absorption of X-rays at energies near an absorption edge.

X-ray Absorption Spectroscopy: A technique used to study the electronic and atomic structure of materials by measuring the absorption of X-rays at different energies.

X-ray Crystallography: A technique used to determine the atomic and molecular structure of a crystal by analyzing the diffraction pattern of X-rays.

X-ray Diffraction: A technique used to determine the atomic and molecular structure of crystalline materials by analyzing the diffraction pattern produced when X-rays interact with the crystal lattice.

X-ray Diffraction: A technique used to determine the atomic and molecular structure of crystalline materials by analyzing the diffraction pattern produced when X-rays interact with the crystal lattice.

X-ray Fluorescence (XRF): An analytical technique used to determine the elemental composition of a sample by measuring the characteristic X-rays emitted upon irradiation with high-energy X-rays.

X-ray Fluorescence Spectroscopy (XRF): An analytical technique used to determine the elemental composition of a sample by measuring the characteristic X-rays emitted upon irradiation with high-energy X-rays.

X-ray Photoelectron Spectroscopy (XPS): A surface-sensitive analytical technique used to measure the elemental composition and chemical state of materials by analyzing the kinetic energy of photoelectrons emitted upon X-ray irradiation.

X-ray Photoelectron Spectroscopy (XPS): A surface-sensitive analytical technique used to measure the elemental composition and chemical state of materials by analyzing the kinetic energy of photoelectrons emitted upon X-ray irradiation.

Xylan: A polysaccharide found in plant cell walls, composed of xylose units joined by beta-1,4 glycosidic bonds.

Xylene: A mixture of three isomeric aromatic hydrocarbons (ortho-, meta-, and para-xylene), used as a solvent, precursor to polymers, and in the production of terephthalic acid.

Xylene: A mixture of three isomeric aromatic hydrocarbons (ortho-, meta-, and para-xylene), used as a solvent, precursor to polymers, and in the production of terephthalic acid.

Xylenol: Any of several isomeric compounds derived from phenol and xylenes, used as disinfectants, antiseptics, and in the production of resins and plastics.

Xylenol: Any of several isomeric compounds derived from phenol and xylenes, used as disinfectants, antiseptics, and in the production of resins and plastics.

Xylose: A five-carbon sugar (pentose) found in plant materials and used in biochemical research and as a food additive.

Xylose: A five-carbon sugar (pentose) with the chemical formula C5H10O5, commonly found in plant materials and used in biochemical research.

Yardang: A streamlined landform created by the erosion of soft rock material by wind action, commonly found in arid and desert regions.

Yarrowia lipolytica: A yeast species used in biotechnology for the production of lipids, enzymes, and biofuels, as well as in waste treatment and bioremediation.

Yeast Autolysate: A mixture of cell components released from yeast cells during autolysis, used as a source of nutrients and flavor compounds in food and beverage production.

Yeast Extract: A water-soluble mixture of proteins, carbohydrates, vitamins, and minerals derived from yeast cells, commonly used as a nutrient source in microbiological media and cell culture.

Yeast: Single-celled fungi belonging to the class Ascomycota, used in various biotechnological processes including fermentation and baking.

Yield Curve: A graphical representation of the relationship between the yield of a chemical reaction and various reaction conditions, such as temperature, pressure, and concentration.

Yield Point: The point on a stress-strain curve where a material exhibits a sudden increase in strain without a significant increase in stress, indicating the onset of plastic deformation.

Yield Strength: The amount of stress required to permanently deform a material, typically determined by the onset of plastic deformation in a stress-strain curve.

Yield Stress Fluid: A type of non-Newtonian fluid that behaves like a solid at low stresses but flows like a liquid at higher stresses.

Yield Stress: The minimum stress required to initiate flow in a viscoelastic material, often observed in materials such as gels, pastes, and suspensions.

Yield: The amount of product obtained in a chemical reaction or process, typically expressed as a percentage of the theoretical maximum.

Ylang-Ylang Oil: An essential oil extracted from the flowers of the ylang-ylang tree (Cananga odorata), used in perfumery and aromatherapy.

Ylide: A neutral molecule containing a positively charged atom (such as carbon) and a negatively charged atom (such as phosphorus or sulfur), commonly used in organic synthesis.

Ylidene: A class of compounds containing a divalent group with a positively charged carbon atom and a negatively charged heteroatom.

Ynamine: A functional group containing a carbon-carbon triple bond (C≡C-N), commonly used as a reactive intermediate in organic synthesis.

Yoctomole: A unit of measurement equal to one septillionth of a mole (10^-24 mol), used to quantify extremely small amounts of substances in analytical chemistry.

Yohimbine Hydrochloride: The hydrochloride salt form of yohimbine, a pharmaceutical drug used primarily as a vasodilator and in the treatment of erectile dysfunction.

Yohimbine: An alkaloid compound derived from the bark of the yohimbe tree, used in traditional medicine and studied for its potential pharmacological effects.

Yolk-Shell Structure: A nanostructure composed of a hollow shell encapsulating a core material, commonly used in catalysis, drug delivery, and energy storage applications.

Young’s Modulus: A measure of the stiffness or elasticity of a material, defined as the ratio of stress to strain in the linear region of the stress-strain curve.

Ytterbium: A chemical element with the symbol Yb and atomic number 70, belonging to the lanthanide series and used in various applications including lasers and nuclear reactors.

Ytterbium: A metallic element with the symbol Yb and atomic number 70, used in various applications including nuclear reactors, lasers, and medical imaging.

Yttrium Aluminum Garnet (YAG): A synthetic crystalline material used as a laser gain medium, optical amplifier, and in solid-state lasers.

Yttrium Aluminum Garnet (YAG): A synthetic crystalline material used as a laser gain medium, optical amplifier, and in solid-state lasers.

Yttrium Aluminum Perovskite (YAP): A synthetic crystalline material used in scintillation detectors, lasers, and optical waveguides.

Yttrium Aluminum Perovskite (YAP): A synthetic crystalline material used in scintillation detectors, lasers, and optical waveguides.

Yttrium Barium Copper Oxide (YBCO): A high-temperature superconductor compound with the formula YBa2Cu3O7, used in superconducting magnets and electronic devices.

Yttrium Barium Copper Oxide (YBCO): A high-temperature superconductor compound used in superconducting magnets, power cables, and other applications.

Yttrium Europium Vanadate (YVO4:Eu): A phosphor material used in fluorescent lamps, cathode ray tubes, and other display devices.

Yttrium Europium Vanadate (YVO4:Eu): A phosphor material used in fluorescent lamps, cathode ray tubes, and other display devices.

Yttrium Fluoride (YF3): A compound used as a component in optical coatings, phosphors, and in the production of yttrium metal.

Yttrium Iron Garnet (YIG): A ferrimagnetic material used in microwave devices, magneto-optical recording media, and as a substrate for epitaxial film growth.

Yttrium Iron Garnet (YIG): A ferrimagnetic material used in microwave devices, magneto-optical recording media, and as a substrate for epitaxial film growth.

Yttrium Orthovanadate (YVO4): A compound used in optical applications such as laser crystals, phosphors, and nonlinear optics.

Yttrium Oxide: A compound with the formula Y2O3, used as a precursor for other yttrium compounds, in ceramics, and as a component of phosphors.

Yttrium Silicate: A compound containing yttrium and silicon, used as a component in ceramics, phosphors, and electronic materials.

Yttrium Stabilized Zirconia (YSZ): A ceramic material consisting of zirconium dioxide (ZrO2) stabilized with yttrium oxide (Y2O3), widely used as a solid electrolyte in fuel cells and oxygen sensors.

Yttrium Vanadate: A compound with the formula YVO4, used in optical applications such as laser crystals, phosphors, and nonlinear optics.

Yttrium Zirconium Oxide (YZO): A compound used as a high-temperature ceramic material and as a substrate for thin-film growth in semiconductor devices.

Yttrium: A metallic element with the symbol Y and atomic number 39, commonly used in alloys and phosphors for electronics and lighting applications.

Zeeman Effect: The splitting of spectral lines in the presence of a magnetic field, caused by the interaction between magnetic moments and the external field.

Zelinsky Reaction: A chemical reaction involving the addition of hydrogen cyanide to aldehydes or ketones in the presence of metal cyanides as catalysts.

Zeolite Catalysis: The use of zeolite materials as catalysts in various chemical reactions, including cracking, isomerization, and hydrocarbon transformations.

Zeolite: A crystalline aluminosilicate mineral with a porous structure, used as a catalyst, adsorbent, and ion-exchange medium in various industrial applications.

Zeotropic: Refers to a mixture of substances that exhibit varying boiling points and composition throughout distillation, unlike azeotropic mixtures.

Zero Valent: Denotes an element in a chemical compound with an oxidation state of zero, indicating no gain or loss of electrons.

Zero-Order Reaction: A chemical reaction in which the rate of reaction is independent of the concentration of reactants.

Zero-Point Energy: The lowest possible energy state of a quantum mechanical system, corresponding to the minimum energy of vibrational motion.

Zeta Potential: The electric potential at the shear plane of a particle immersed in a fluid medium, used to characterize colloidal stability and surface charge.

Zinc Acetate: A chemical compound with the formula Zn(CH3COO)2, used in the production of rayon, as a dietary supplement, and in the treatment of diarrhea.

Zinc Carbonate: A chemical compound with the formula ZnCO3, occurring naturally as the mineral smithsonite and used in ceramics and as a dietary supplement.

Zinc Chloride: A chemical compound with the formula ZnCl2, used as a catalyst in organic synthesis, as a dehydrating agent, and in the manufacture of wood preservatives.

Zinc Finger: A protein structural motif characterized by the coordination of one or more zinc ions by cysteine and histidine residues, often involved in DNA binding and protein-protein interactions.

Zinc Nitrate: A chemical compound with the formula Zn(NO3)2, used in the manufacture of zinc oxide, as a mordant in dyeing, and in the production of catalysts.

Zinc Oxide: A white powder compound with the chemical formula ZnO, used in sunscreens, ointments, and as a pigment in paints and ceramics.

Zinc Phosphate: A chemical compound with the formula Zn3(PO4)2, used as a corrosion inhibitor, pigment in paints, and in dental cements.

Zinc Phosphide: A chemical compound with the formula Zn3P2, used as a rodenticide and in fireworks due to its ability to emit light upon oxidation.

Zinc Selenide: A chemical compound with the formula ZnSe, used in infrared optical components, laser windows, and semiconductor devices.

Zinc Silicate: A compound with the formula Zn2SiO4, occurring naturally as the mineral willemite and used as a pigment and in ceramics.

Zinc Stearate: A white, fluffy powder of zinc soap with the formula Zn(C18H35O2)2, used as a lubricant, mold release agent, and in cosmetics.

Zinc Sulfide: A chemical compound with the formula ZnS, occurring naturally as the mineral sphalerite and used in luminescent materials and pigments.

Zinc: A metallic element with the symbol Zn and atomic number 30, commonly used as a coating to prevent corrosion and in various alloys.

Zincate Ion: The anion [Zn(OH)4]2-, formed in solutions containing zinc oxide and alkali hydroxides, commonly used in zinc plating baths.

Zincate Process: An electrochemical process used to deposit zinc coatings onto surfaces, involving the use of alkaline zincate solutions.

Zincate: A compound or ion containing zinc in its highest oxidation state, commonly formed in zinc plating and electrochemical processes.

Zincblende: A mineral with the chemical formula ZnS, occurring naturally as sphalerite and used in the production of zinc and as a semiconductor material.

Zinc-Iron Alloy: A metallic alloy composed of zinc and iron, used as a sacrificial coating to protect steel from corrosion.

Zirconium: A metallic element with the symbol Zr and atomic number 40, widely used in nuclear reactors, alloys, and in the production of zirconium dioxide.

ZnCl2: Chemical formula for zinc chloride, a white crystalline compound used in soldering fluxes, wood preservation, and as a catalyst in organic synthesis.

Zn-Hg Amalgam: A mixture of zinc and mercury used as a reducing agent in organic synthesis and as a dental filling material.

Zn-Mg Alloy: An alloy composed of zinc and magnesium, known for its lightweight properties and corrosion resistance, used in aerospace and automotive industries.

Zone Refining: A purification technique used to obtain high-purity metals by passing a molten zone through a solid crystalline material.

Zwischenion: A transient intermediate species formed during a chemical reaction, typically highly reactive and short-lived.

Zwitterion: A molecule that contains both positively and negatively charged functional groups, resulting in overall neutrality.

Zwitterionic Polymer: A polymer containing both positively and negatively charged functional groups, often used in biomaterials and drug delivery systems.

Zwitterionic Surfactant: A surfactant molecule containing both positively and negatively charged functional groups, commonly used in personal care products and detergents.

Zwitterionic Surfactant: A type of surfactant molecule containing both positively and negatively charged functional groups, used in detergents and personal care products.