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960 terms · page 29 of 40
Period
A horizontal row of the periodic table, corresponding to one principal quantum number of the valence shell.
Atomic Structure & PeriodicityPeriodic Law
The principle that the properties of the elements are periodic functions of their atomic numbers.
Atomic Structure & PeriodicityPeriodic Table
The tabular arrangement of the chemical elements by increasing atomic number, grouping those with similar properties in vertical columns.
Chemical EquilibriumPerturbation and Re-equilibration
The disturbance of an equilibrium followed by its relaxation to a new equilibrium state.
Acids, Bases & SaltspH
The negative logarithm to base ten of the hydrogen ion concentration, measuring the acidity of a solution.
Acids, Bases & SaltspH Scale
The conventional scale, usually running from 0 to 14, on which the acidity or alkalinity of aqueous solutions is expressed.
States of Matter & Gas LawsPhase Diagram
A pressure–temperature plot showing which phase of a substance is thermodynamically stable under any given conditions.
Chemical EquilibriumPhase Equilibrium
The condition in which two or more phases of a substance coexist with no net transfer between them.
Organic ChemistryPhenol
A compound in which a hydroxyl group is bonded directly to an aromatic ring.
Acids, Bases & SaltsPhenolphthalein
An acid–base indicator that is colourless in acid and pink in alkaline solution, changing between pH 8.3 and 10.0.
Biochemistry & Polymer ChemistryPhospholipid
A lipid in which one fatty acid of a triglyceride is replaced by a phosphate-containing group.
Chemical Kinetics & CatalysisPhotochemical Quantum Yield
The number of molecules reacting for each photon of light absorbed by the system.
Stoichiometry & Chemical ReactionsPhotochemical Reaction
A reaction initiated by the absorption of light, which promotes a molecule to an electronically excited state.
Biochemistry & Polymer ChemistryPhotosynthesis
The process by which plants use light energy to convert carbon dioxide and water into carbohydrate and oxygen.
Foundations of ChemistryPhysical Change
A change that alters the form or state of a substance while leaving its chemical composition intact.
Chemical EquilibriumPhysical Equilibrium
An equilibrium between two physical states or phases of the same substance.
Foundations of ChemistryPhysical Property
A characteristic of a substance that can be observed or measured without altering its chemical identity.
Chemical Kinetics & CatalysisPhysisorption
Weak adsorption in which molecules are held to a surface by van der Waals forces alone.
Chemical Bonding & Molecular StructurePi Bond
A covalent bond formed by the sideways overlap of parallel p orbitals, with electron density above and below the internuclear axis.
Acids, Bases & SaltspKa
The negative logarithm of the acid dissociation constant, giving a convenient scale of acid strength.
Acids, Bases & SaltspKb
The negative logarithm of the base dissociation constant.
States of Matter & Gas LawsPlasma
A state of matter consisting of a hot, electrically conducting mixture of ions and free electrons.
Atomic Structure & PeriodicityPlum Pudding Model
J. J. Thomson's 1904 model picturing the atom as a sphere of diffuse positive charge with electrons embedded within it.
Acids, Bases & SaltspOH
The negative logarithm of the hydroxide ion concentration.