Explain why lattice energy of magnesium oxide (MgO) is higher than that of magnesium chloride (MgCl2)

Magnesium oxide has high lattice energy because

• Magnesium ions and oxygen ion are bonded by a double bond that is stronger than a single bond between chloride ions and magnesium ions.
• O^2- (126pm) is smaller than Cl^– (167pm)and O^2- is less polarized than Cl^–. Thus the ionic bond formed between Mg²⁺ and O^2- ions are more ionic and stronger than those formed between Mg²⁺ and Cl^–.