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A–Z
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Chemical Equilibrium

Overall Formation Constant

The equilibrium constant for the formation of a complex directly from the free metal ion and all its ligands.

β_n = K₁K₂ … K_n Various
Chemical Kinetics & Catalysis

Overall Order

The sum of the individual orders with respect to every reactant appearing in the rate law.

n = m₁ + m₂ + … Dimensionless
Electrochemistry & Redox

Overpotential

The extra voltage beyond the theoretical value that must be applied before an electrode reaction proceeds at a useful rate.

η = E_applied − E_equilibrium V
Electrochemistry & Redox

Oxidation

The loss of electrons by a species, accompanied by an increase in its oxidation number.

M → Mⁿ⁺ + n e⁻ Dimensionless
Electrochemistry & Redox

Oxidation Number

The hypothetical charge an atom would carry if all its bonds were treated as fully ionic.

Σ oxidation numbers = overall charge Dimensionless
Stoichiometry & Chemical Reactions

Oxidation Number Method

A technique for balancing redox equations by equating the total increase and decrease in oxidation numbers.

Σ increase = Σ decrease Dimensionless
Organic Chemistry

Oxidation of Alcohols

The conversion of alcohols to carbonyl compounds or carboxylic acids by removal of hydrogen.

R–CH₂OH → RCHO → RCOOH Dimensionless
Electrochemistry & Redox

Oxidising Agent

A species that accepts electrons from another substance and is itself reduced in the process.

V
Acids, Bases & Salts

Oxoacid

An acid in which the ionisable hydrogen is attached to oxygen, which in turn is bonded to a central atom.

HₙXOₘ Dimensionless
Atomic Structure & Periodicity

p-Block Elements

The elements of groups 13 to 18, in which the outermost electrons progressively fill p orbitals.

ns² np¹⁻⁶ Dimensionless
States of Matter & Gas Laws

Packing Efficiency

The percentage of the total volume of a unit cell that is actually occupied by the constituent particles.

(volume of atoms / cell volume) × 100 Dimensionless
Atomic Structure & Periodicity

Paramagnetism

Weak attraction into a magnetic field, shown by substances containing one or more unpaired electrons.

μ = √(n(n+2)) BM BM
Nuclear & Radiochemistry

Parent and Daughter Nuclide

The nuclide undergoing decay and the nuclide produced by that decay.

parent → daughter + radiation Dimensionless
States of Matter & Gas Laws

Partial Pressure

The pressure that one component of a gas mixture would exert if it alone occupied the whole volume.

p_i = x_i × p_total Pa
Chemical Equilibrium

Partition Coefficient

The equilibrium ratio of a solute's concentrations in two immiscible phases.

P = C₁ / C₂ Dimensionless
Solutions & Colligative Properties

Parts per Billion

A concentration unit expressing one part of solute per thousand million parts of solution.

ppb = (m_solute / m_solution) × 10⁹ ppb
Solutions & Colligative Properties

Parts per Million

A concentration unit expressing one part of solute per million parts of solution by mass or volume.

ppm = (m_solute / m_solution) × 10⁶ ppm
Thermochemistry & Thermodynamics

Path Function

A quantity whose value depends on the specific route taken between two states.

δq, δw J
Atomic Structure & Periodicity

Pauli Exclusion Principle

The rule that no two electrons in an atom may have the same set of all four quantum numbers.

n, l, mₗ, mₛ must differ Dimensionless
Nuclear & Radiochemistry

Penetrating Power

The depth to which a given type of radiation can travel into a material before being absorbed.

mm
Biochemistry & Polymer Chemistry

Peptide Bond

The amide linkage joining the carboxyl group of one amino acid to the amino group of the next.

–CO–NH– Dimensionless
Foundations of Chemistry

Percentage Composition

The proportion by mass of each element in a compound, expressed as a percentage of the total mass.

% element = (n × A_r / M_r) × 100 Dimensionless
Stoichiometry & Chemical Reactions

Percentage Purity

The proportion of a sample that consists of the desired compound, expressed as a percentage of the total mass.

% purity = (mass pure / mass sample) × 100 Dimensionless
Stoichiometry & Chemical Reactions

Percentage Yield

The actual yield expressed as a percentage of the theoretical yield.

% yield = (actual / theoretical) × 100 Dimensionless