First Ionisation Energy
- The ionisation energy (IE) of an element is the amount of energy required to remove one mole of electrons from one mole of atoms of an element in the gaseous state to form one mole of gaseous ions
- Ionisation energies are measured under standard conditions which are 298 K and 100 kPa
- The units of IE are kilojoules per mole (kJ mol-1)
- The first ionisation energy is the energy required to remove the one mole of electrons from one mole the gaseous atoms
- E.g. the first ionisation energy of calcium:
Ca(g) → Ca+ (g) + e- 1st ∆H I.E. = +590 kJ mol-1