Which equation represents the second ionization energy of potassium?

A.     ${\text{K(g)}} \to {{\text{K}}^{2 + }}{\text{(g)}} + {\text{2}}{{\text{e}}^ - }$

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

C.     ${\text{K(s)}} \to {{\text{K}}^{2 + }}{\text{(g)}} + {\text{2}}{{\text{e}}^ - }$

D.     ${{\text{K}}^ + }{\text{(s)}} \to {{\text{K}}^{2 + }}{\text{(g)}} + {{\text{e}}^ - }$

B