2 Born-Haber Cycles enthalpy H magnesium chloride MgCl 2 (s) Mg 2+ (g) + 2Cl - (g) H lattice association Mg (s) + Cl 2 (g) H formation H atomisation Mg (g) + Cl 2 (g) H first ionisation energy Mg + (g) + e - + Cl 2 (g) Mg 2+ (g) + 2e - + 2Cl (g) H second ionisation energy 2 x H first electron affinity Mg 2+ (g) + 2e - + Cl 2 (g) H bond energy of chlorine