Question

Which of the following is an example of a positive ion and negative ion that is isoelectronic with argon?

• A. $K^{+}$ and $C{l}^{-}$ or $C{a}^{2+}$ and $S^{2-}$
• B. $N{a}^{+}$ and $F^{-}$ or $M{g}^{2+}$ and $O^{-}$
• C. $K^{+}$ and $I^{-}$ or $M{g}^{2+}$ and $S^{2-}$
• D. $K^{+}$ and $I^{-}$ or $C{a}^{2+}$ and $O^{2-}$

Answer 1

The correct option is A $K^{+}$ and $C{l}^{-}$ or $C{a}^{2+}$ and $S^{2-}$

Element Atomic no. Ion Number of electrons
$K$ 19 $K^{+}$ 18
$Cl$ 17 $C{l}^{-}$ 18
$Ca$ 20 $C{a}^{2+}$ 18
$S$ 16 $S^{2-}$ 18

All are isoelectronic with argon. Iso electronic species are elements having the same number of electrons