# Given MgO, Li_2O, MgCl_2, and NaO, why should MgO have the highest lattice enthalpy?

$M {g}^{2 +}$ is the smallest cation, and also it is the only that is a dication. Oxide anion is also the smallest anion, and it is the only that is a dianion. On this basis, the ionic bond(s) formed between magnesium and oxide ions should be of the greatest magnitude.