Energetics Definitions

enthalpy of formation

enthalpy change when one mole of a substance is formed from its constituent elements with all substances in their standard states

enthalpy of combustion

enthalpy change when one mole of a substance undergoes complete combustion in oxygen with all substances in standard states

enthalpy of neutralisation

enthalpy change when one mole of water is formed in a reaction between an acid and akali under standard conditions

1st ionisation enthalpy

enthalpy change when each atom in one mole of gaseous atoms loses one electron to form one mole of gaseous 1+ ions

1st electron affinity

enthalpy change when each atom in one mole of gaseous atoms gains one electron to form one mole of gaseous 1- ions

enthalpy of atomisation

enthalpy change when one mole of gaseous atoms is produced from an element in its standard state

hydration enthalpy

enthalpy change when one mole of gaseous ions become hydrated (surrounded by water molecules)

enthalpy of solution

enthalpy change when one mole of an ionic solid dissolves in water so that the dissolved ions are well separated and do not interact with each other

mean bond dissociation enthalpy

enthalpy change when one mole of covalent bonds is broken in the gaseous state, averaged over different molecules

lattice enthalpy of formation

enthalpy change when one mole of a solid ionic compound is formed from its constituent ions in the gas phase

lattice enthalpy of dissociation

enthalpy change when one mole of a solid ionic compound is broken up into its constituent ions in the gas phase

enthalpy of vaporisation

enthalpy change when one mole of a liquid is turned into a gas

enthalpy of fusion

enthalpy change when one mole of a solid is turned into a liquid

enthalpy change

heat energy change at constant pressure

polarisation

the distortion of the electron cloud in a molecule or ion by a nearby positive charge

polarising power

the ability of a positive ion to distort the electron cloud of a neighbouring negative ion

polarisability

an indication of the extent to which the electron cloud in a molecule or an ion can be distorted by a nearby electron charge