Even though so much energy is required to form a metal cation with a 2+ charge, the alkaline earth metals form halides with general formula MX₂, rather than MX.
(a) Use the following data to calculate ΔH° f MgCl
Mg(s) → Mg(g) ΔH° = 148 kJ
Cl₂(g) → 2Cl(g) ΔH° = 243 kJ
Mg(g) → Mg⁺(g) + e⁻ ΔH° = 738 kJ
Cl(g) + e⁻ → Cl⁻ (g) ΔH° = -349 kJ
ΔH° lattice of MgCl = 783.5 kJ/mol