Chemistry

First ionisation energy

The energy required to remove one mole of electrons from one mole of gaseous atoms.

Factors affecting ionisation energy

Across a period: General increase, shielding remains the same, nuclear charge increases, atomic radius decreases, nuclear attraction increases.

Down a group: Decreases, nuclear charge increase is outweighed by increased atomic radius and increased shielding, nuclear attraction decreases.

Successive ionisation energy

The energy required to remove each electron one-by-one from one mole of gaseous atoms / ions.

Second ionisation energy

The removal of one mole of electrons from one mole of gaseous 1+ ions to form one mole of 2+ ions.

Average bond enthalpy

The energy required to break one mole of gaseous bonds.

Enthalpy change of combustion

The enthalpy change that takes place when one mole of a substance is completely combusted.

Enthalpy change of formation

The enthalpy change that takes place when one mole of a compound is formed from its constituent elements.

Enthalpy change of neutralisation

The enthalpy change that takes place when one mole of a compound is formed from its elements.

Enthalpy change of reaction

The enthalpy change that is associated with a particular chemical equation.

Standard conditions

100kPa, 298K

Catalyst

A substance that speeds up the rate of a reaction without being used up, allows the reaction to proceed via a different route by lowering activation energy, processes can take place at lower temperatures → less energy is required (decreases combustion of fossil fuels = CO2 emissions are reduced).