As you move vertically down a column, the size of the ions of the same charge increases. It is called aluminum chloride. O. It is called sodium oxide. It is called strontium fluoride. It is called calcium sulfide.
Lattice energies become more exothermic for small ion sizes and greater ionic charges.
Because the Br ion is smaller than the I ion, NaBr will have the more exothermic lattice energy. Because BaCl 2 contains an anion of 1 charge and BaO contains an anion of 2 charge, BaO will have the more exothermic lattice energy. K 2 O contains an anion of 2 charge, K 2 O will have the more exothermic lattice energy. Therefore, Li 2 O has the more exothermic lattice energy. Remember that lattice energies are more exothermic as you increase ionic charge or decrease ionic radii.