a. For each of the following pairs of compounds, state with reasons which one you would expect to have the higher lattice energy.

i. NaCl and KBr

ii. KCl and SrS.

b. In some crystal lattices, some of the ions are polarised.

i. State the meaning of the term ion polarisation.

ii. Explain why a magnesium ion is better than a sodium ion at polarising an iodide ion.

iii. Use ideas about ion polarisation to explain why barium carbonate is more stable to thermal decomposition than magnesium carbonate.