Atomic Structure

Ionisation Energy

The energy to remove one electron from every atom in one mole of gaseous atoms in an element

• greater atomic radius the smaller the nuclear attraction experienced by the outer electrons = lower ionisation energy

• the greater the nuclear charge the greater the attractive force on the outer electrons = higher ionisation energy

• more inner shells so more shielding therefore smaller attraction between nucleus and outer electrons = lower ionisation energy

Equations for ionisation energy must always write the element as a gas

Argon has the highest first ionisation energy in period 3 because it has the highest nuclear charge