Browse All 960 Chemistry Terms A–Z

Glycosidic Bond Biochemistry & Polymer Chemistry Dimensionless The covalent linkage joining a sugar unit to another molecule through an oxygen bridge. C–O–C

Graham's Law of Diffusion States of Matter & Gas Laws Dimensionless The rate at which a gas diffuses or effuses is inversely proportional to the square root of its molar mass. r₁ / r₂ = √(M₂ / M₁)

Gravimetric Analysis Analytical Chemistry & Spectroscopy g Quantitative analysis based on measuring the mass of a product of known composition. % analyte = (m_precipitate × factor / m_sample) × 100

Gray Nuclear & Radiochemistry Gy The SI unit of absorbed radiation dose, equal to one joule of energy deposited per kilogram of matter. 1 Gy = 1 J/kg

Grignard Reagent Organic Chemistry Dimensionless An organomagnesium halide that acts as a source of a carbanion-like nucleophilic carbon. R–Mg–X

Group Atomic Structure & Periodicity Dimensionless A vertical column of the periodic table whose members share the same valence electron configuration.

Half-Life of a Reaction Chemical Kinetics & Catalysis s The time required for the concentration of a reactant to fall to half its initial value. t½ = 0.693 / k (first order)

Half-Reaction Electrochemistry & Redox Dimensionless An equation showing either the oxidation or the reduction part of a redox process, including the electrons transferred. Ox + n e⁻ ⇌ Red

Half-Reaction Method Stoichiometry & Chemical Reactions Dimensionless A technique for balancing redox equations by splitting them into separate oxidation and reduction half-equations. balance atoms, then O with H₂O, H with H⁺, charge with e⁻

Haloalkane Organic Chemistry Dimensionless An alkane in which one or more hydrogen atoms have been replaced by halogen atoms. R–X (X = F, Cl, Br, I)

Halogens Atomic Structure & Periodicity Dimensionless The group 17 elements — fluorine through astatine — which are one electron short of a full outer shell. ns² np⁵

Heat Thermochemistry & Thermodynamics J Energy transferred between a system and its surroundings solely because of a temperature difference. q = mcΔT

Heat Capacity at Constant Pressure Thermochemistry & Thermodynamics J/(mol·K) The heat needed to raise a system's temperature by one kelvin while pressure is held constant. C_p = C_V + R (ideal gas)

Heat Capacity at Constant Volume Thermochemistry & Thermodynamics J/(mol·K) The heat needed to raise a system's temperature by one kelvin while its volume is held fixed. C_V = (∂U/∂T)_V

Heisenberg Uncertainty Principle Atomic Structure & Periodicity J·s The principle that the position and momentum of a particle cannot both be known to arbitrary precision at the same time. Δx · Δp ≥ h / 4π

Helmholtz Free Energy Thermochemistry & Thermodynamics kJ/mol The thermodynamic potential that determines spontaneity at constant temperature and volume. A = U − TS

Henderson–Hasselbalch Equation Acids, Bases & Salts Dimensionless The equation giving the pH of a buffer from the pKa of its acid and the ratio of conjugate base to acid. pH = pKa + log([A⁻]/[HA])

Henry's Law Solutions & Colligative Properties Pa The solubility of a gas in a liquid is directly proportional to the partial pressure of that gas above the liquid. p = K_H × x

Hess's Law Thermochemistry & Thermodynamics kJ/mol The total enthalpy change of a reaction is the same regardless of the route taken, provided the initial and final states are identical. ΔH_total = ΣΔH_steps

Heterogeneous Catalysis Chemical Kinetics & Catalysis Dimensionless Catalysis in which the catalyst is in a different phase from the reactants, usually a solid with gaseous or liquid reagents.

Heterogeneous Equilibrium Chemical Equilibrium Dimensionless An equilibrium involving species present in more than one phase.

Heterogeneous Mixture Foundations of Chemistry Dimensionless A mixture in which the components remain physically distinct, so composition varies from one region of the sample to another.

Hexagonal Close Packing States of Matter & Gas Laws Dimensionless A close-packed arrangement in which layers of spheres repeat in an ABAB sequence. 6 atoms per cell, 74% packing

High Spin Complex Inorganic & Coordination Chemistry BM A complex in which electrons occupy the higher d orbitals singly before pairing, maximising unpaired spins. Δ < P

Browse the dictionary