Chem A2 definitions

Transition element

forms one or more stable ions with partially filled 3d-subshell

Coordination number

The number of dative bonds between the ligand and the central metal ion

Optimally active

A substance that is able to rotate the plane of polarised light in opposite directions

Standard Electrode Potential

voltage of an electrode compared to standard hydrogen electrode under standard conditions

Monodenate ligand

forms a single / one dative bond to a central metal ion with lone pair

Standard conditions

1 moldm-3

1 atm

298k

Buffer solution

A solution which resists changes in pH when small amounts of acid (H+) or alkali (OH-) are added

complex ion

a molecule or ion formed by a central metal ion bonded to ligands

polydentate ligand

a species that donates many lone pairs to form many dative bond to a metal ion

partition coefficient, K_pc

ratio of the concentration of a solute in the two immiscible solvents /liquids at equilibrium

electron affinity

energy change when one electron is added to each atom in one mole of gaseous atoms

lattice energy

energy change when 1 mole of an ionic compound is formed from gaseous ions

standard cell potential

potential difference between two half-cells under standard conditions

rate-determining step

slow(est) step

mathematical expression pH

–log₁₀[H⁺]

mathematical expression K_w

[H⁺][OH^–]

bidentate ligand

a species that donates two lone pairs to form two dative bonds to a metal ion

ligand

a species that shares a lone pair of electrons to form a coordinate bond to a metal ion

entropy (of a system)

the number of possible arrangements of the particles and their energy (in a given system)

order of reaction

the power to which a concentration of a reactant is raised in the rate equation

half-life of a reaction

time taken for the concentration / mass / amount of a reactant to halve

enthalpy change of solution

enthalpy change when one mole of a solute and dissolves in water to form a solution of infinite dilution

isoelectric point

pH at which a molecule has no overall charge and can exist as a zwitterion

stability constant, K_stab

the equilibrium constant for the formation of the complex ion in a solvent

first electron affinity

enthalpy change when one mole of electrons are gained by one mole of gaseous atoms to form one mole of gaseous -1 ions

enthalpy change of hydration

energy change when one mole of gaseous ions dissolves in water

homogeneous catalyst

the catalyst and the reactants are in the same state

heterogeneous catalyst

the catalyst and the reactants are in a different state

racemic mixture

a mixture containing equal amounts of each optical isomer

enthalpy change of atomisation

enthalpy change when one mole of gaseous atoms formed from the element (in its standard state at 298 K)

retention time

the time that the substance stays in the column

time between injection and detection

conjugate acid–base pairs

species that differ (by the presence or absence) of a H+ ion / proton

degenerate orbital

orbitals of the same energy

non degenerate orbital

orbitals of different energy