Question

The number of d-electrons in `Fe^(2+)`(Z=26) is not equal to the number of electrons in which one of the following ?
A. s-electrons in Mg (Z=12)
B. p-electrons in Cl (Z=17)
C. d-electrons in Fe (Z=26)
D. p-electrons in Ne (Z=10)

Answer 1

Correct Answer - B
(b) Electronic configuration of `Fe^(2+)` is [Ar] `3d^(6) 4s^(0)`.
`:.` Number of electrons = 6
Mg - `1s^(2) 2s^(2)2p^(6)3s^(2)` (6s electrons)
It matches with the 6d electrons of `Fe^(2+)`
`Cl - 1s^(2) 2s^(2)2p^(6)3s^(2)3p^(5)` (11 p electrons)
It does not match with the 6d electrons of `Fe^(2+)`
Fe - [Ar] `3d^(6) 4s^(2)` (6d electrons)
It does not match with the 6d electrons of `Fe^(2+)`
Ne - `1s^(2) 2s^(2)2p^(6)` (6 p electrons)
It matches with the 6d electrons of `Fe^(2+)` .
Hence, Cl had 11p electrons which does not matches in number with 6d electrons of `Fe^(2+)`.