Ionisation Energy

Question 1

Define ionisation energy

Answer 1

Energy required to remove the outermost electron from each atom in one mole of gaseous atoms to form one mole of gaseous ions with a charge of +1. Unit for ionisation energy kJ/mol.

Question 2

Describe the 3 factors that affect ionisation energy.

Answer 2

1. The distance of the electrons from the nucleus
   - down the group - electrons are further away from the nucleus
   - experience more shielding
   - weaker nuclear attraction
   - lower ionisation energy
2. Nuclear charge
   - across the period - increase in proton number
   - stronger attraction
   - higher ionisation energy
   - similar shielding across a period
3. Spin-pair repulsion (paired electrons)
   - paired electrons repel each other
   - easier to remove one electron
   - lower ionisation energy

Question 3

What is the rule for ionisation energy?

Answer 3

The biggest jump in ionisation energy occurs when an electron is removed from a shell closer to the nucleus