Approximate ionic radii (pm) are provided below.
Li⁺ 90 Mg²⁺ 72 Ca²⁺ 100 Al³⁺ 54
O²⁻ 140 S²⁻ 184 N³⁻ 146
Using these values, rank the following compounds in order of INCREASING magnitude of lattice energy.
I. Li₂O II. MgO III. CaS IV. AlN
a) I < II < III < IV
b) I < III < II < IV
c) III < I < II < IV
d) III < II < I < IV