Question

Consider the given box:

$\begin{array}{c}C{l}^{-},Ar,K^{+},O^{2-},M{g}^{2+},F^{-}\end{array}$

The total number of species which are isoelectronic with $C{a}^{2+}$ is

• A.
  1
• B.
  2
• C.
  3
• D.
  4

Answer 1

The correct option is C

3
The species in which the number of electrons are the same are known as isoelectronic species.



$\begin{array}{cc}\text{Species}& \text{Number of electrons}\\ C{a}^{2+}& \text{18}\\ C{l}^{-}& \text{18}\\ \text{Ar}& \text{18}\\ \text{(}{K}^{+}\text{)}& \text{18}\\ O^{2-}& \text{10}\\ M{g}^{2+}& \text{10}\\ F^{-}& \text{10}\end{array}$

The calcium ion, $C{a}^{2+}$ has 18 electrons. Three species, i.e., $C{l}^{–},Arand{K}^{+}$ also have 18 electrons and hence, are isoelectronic with $C{a}^{2+}$.

Hence, the correct answer is option (c) .