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.
(c) Use Hess’s law to calculate ΔH° for the converion MgC₁ to MgCl₂ and Mg( ΔH°f MgCl₂ = - 2641.6 kJ/mol).