The electronic configurations of `Cr^24` and `Cu^29` are abnormal -

Options

A. Due to extra stability of exactly half filled and exactly fully filled sub shells
B. Because they belong to d-block
C. both (a) and (b)
D. None of the above

Answer

A

Explanation

(a) `Cr_24 - 1 s^2 2 s^2 2 p^6 3 s^2 4 s^2 3 d^4`
(original configuration)
but `- d^5 -` its's half-filled state and that is state most stable than other state.
`Cr_24 - 1 s^2 2 s^2 2 p^6 3 s^6 4 s^1 3 d^5`
As above full filled stata that is most stable than other state.
`Cu - 1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^2 3 d^9`
but `1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^1 3 d^10` (full filled).