Question

Which pair is of isoelectronic species?

• A. $K^{+},C{l}^{-},N{a}^{+}$
• B. $K^{+},C{l}^{-},C{a}^{2+}$
• C. $F{e}^{-},A{l}^{3+},K^{+}$
• D. $F{e}^{2+},C{u}^{2+},V^{3+}$

Answer 1

Answer: (B)

Isoelectronic species have same number of electrons.

$K^{+}:$ Number of electrons $=19-1=18$

${}_{17}C{l}^{-}:$ Number of electrons $=17+1=18$

${}_{20}C{a}^{2+}:$ Number of electrons $=20-2=18$

hence, $K^{+},C{l}^{-}$ and $C{a}^{2+}$ are isoelectronic species.