Which equation best represents the first ionization energy of magnesium?

A.     ${\text{Mg(s)}} \to {\text{M}}{{\text{g}}^ + }{\text{(s)}} + {{\text{e}}^ - }$

B.     ${\text{Mg(g)}} \to {\text{M}}{{\text{g}}^{2 + }}{\text{(g)}} + {\text{2}}{{\text{e}}^ - }$

C.     ${\text{Mg(g)}} \to {\text{M}}{{\text{g}}^ + }{\text{(g)}} + {{\text{e}}^ - }$

D.     ${\text{Mg(s)}} \to {\text{M}}{{\text{g}}^ + }{\text{(g)}} + {{\text{e}}^ - }$

C