Keeping in mind the concept of charge density, compound having highest lattice energy is

Explanation

Lattice energy is the energy required to completely separate one mole of a solid ionic compound into its gaseous ions. It is influenced by both the charges of the ions and the distances between them.The charge density is higher when the charges are larger and the ions are smaller. In the given options:KCl (potassium chloride): K⁺ and Cl⁻ ions are involved.MgO (magnesium oxide): Mg²⁺ and O²⁻ ions are involved.LiBr (lithium bromide): Li⁺ and Br⁻ ions are involved.NaF (sodium fluoride): Na⁺ and F⁻ ions are involved.Among these, Mg²⁺ and O²⁻ ions in MgO have higher charges and smaller sizes compared to the other ions in the options. Higher charge density leads to higher lattice energy. Therefore, MgO has the highest lattice energy among the given compounds. Therefore, the correct answer is (b) MgO.