The sequence of filling electron in sub-shells of element with few exception in d-block and f-block element is governed by Aufbau principal followed by Hund's rule and pauli's exclusion principal
a. The electron prefers to enter into sub-shell with lower `(n +l)` values
The energy for any sub-shell of an element other than hydrogen is proportional to the sum of principal quantum number (n) and angular momentum quantum number
b. If `(n + l)` value is same for many sub-shell with lowest n value
c. i. Fulfilled sub-shell is most stable
ii. Half filled sub-shell is more stable less than half filed
Which pair of element follow rule (c ) (ii) ?

Options

A. `_(28)Cu`
B. `_(24)Cr`
C. `_(28)Fe`
D. `_(23)Cu`

Answer

A

Explanation

`_(28)Cu`