a. The first ionisation energies of four consecutive elements in the Periodic Table are: sodium = 494 kJ mol^–1

magnesium = 736 kJ mol^–1

aluminium = 577 kJ mol^–1

silicon = 786 kJ mol^–1
i. Explain the general increase in ionisation energies from sodium to silicon.

ii. Explain why aluminium has a lower first ionisation energy than magnesium.

b. The first ionisation energy of fluorine is 1680 kJ mol^–1 whereas the first ionisation energy of iodine is 1010 kJ mol^–1. Explain why fluorine has a higher first ionisation energy than iodine despite it having a smaller nuclear charge.