Final answer:
The lattice energy of an ionic solid decreases as the sizes of the ions increase.
Step-by-step explanation:
The lattice energy of an ionic solid decreases as the sizes of the ions increase.
This is because the lattice energy is inversely related to the internuclear distance and is proportional to the charge of the ions. As the size of the ions increases, the internuclear distance also increases, decreasing the lattice energy.
For example, the lattice energy of LiF (Z* and Z¯ = 1) is 1023 kJ/mol, whereas that of MgO (Z* and Z = 2) is 3900 kJ/mol.