$\begin{array}{lcc}\hline \text { Ions } & {\text { Atomic number }} & {\text { Number of electrons }} \\ \hline 0^{2-} & {8} & {10} \\ {\mathrm{F}^{-}} & {9} & {10} \\ {\mathrm{Na}^{+}} & {11} & {10} \\ {\mathrm{Mg}^{2+}} & {12} & {10} \\ \hline\end{array}$