Pick up the correct statement about the following pairs
I : Ar and `S^(2-)`, II: Fe and `Ni^(2+)`
(At. No. Ar = 18, S = 16, Fe = 26, Ni = 28)

Options

A. Both of these pairs contain isoelectronic species
B. Only pair (I) is isoelectronic
C. Only pair (II) is isoelectronic
D. None of the pair is isoelectronic.

Answer

B

Explanation

(I) Both Ar and `S^(2-)` have `1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6)` configuration
(II) `Fe(Z = 26) : 1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6) 4s^(2) 3d^(6)`
`Ni^(2+) (Z = 28) : 1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6) 3d^(8)`
As such Fe and `Ni^(3+)` are not isoelectronic.