Iso-electronic species are

Isoelectronic species are known as atoms or ions that have the same number of electrons

. $$\begin{gathered} {\mathrm{F}}^{-}=9+1=10{\mathrm{e}}^{-} \\ {\mathrm{O}}^{2-} = 8+2 =10{\mathrm{e}}^{-} \end{gathered}$$