(9分)用下列数据求氧原子的电子亲和能
Mg(s)Mg(g)    ΔH₁="141" kJ·mol^-1
Mg(g)Mg²⁺(g)  ΔH₂="2" 201 kJ·mol^-1
O²O(g)     ΔH₃="247" kJ·mol^-1
Mg²⁺(g)+O^2-(g)MgO(s)    ΔH₄="-3" 916 kJ·mol^-1
Mg(s)+O₂(g)MgO(s)   ΔH₅="-602" kJ·mol^-1