During a comparison of experimental and theoretical lattice enthalpies for MgO, the experimental value is 1800 kJ mol⁻¹ and the theoretical value is 1700 kJ mol⁻¹. What does this discrepancy suggest about the covalent character of the MgO bond, and how would you justify your conclusion using lattice enthalpy concepts?

A lower theoretical lattice enthalpy than the experimental value indicates that the real crystal releases more energy than predicted by the ideal point‑charge model. This excess energy release suggests that the MgO bond has a greater covalent character than assumed in the theoretical calculation, which treats the ions as purely ionic. The stronger covalent interaction increases the lattice energy beyond the purely ionic estimate, leading to the experimental value being higher.

The answer defines both experimental and theoretical lattice enthalpies, identifies the key difference (experimental > theoretical), explains when each applies (real crystal vs idealised model), and concludes that the discrepancy indicates increased covalent character. This assesses the student’s ability to interpret lattice enthalpy data in terms of bond character.