Question

The outer electron configuration of Gd (Atomic No. 64) is :

• A. $4f^{3}5d^{5}6s^2$
• B. $4f^{4}5d^{0}6s^2$
• C. $4f^{2}5d^{4}6s^2$
• D. $4f^{7}5d^{1}6s^2$

Answer 1

The correct option is D $4f^{7}5d^{1}6s^2$

Half-filled stabled configuration will be more favoured to $Gd$. Arrange the orbitals according to the increasing energy.
The configuration of $Gd$ is $\left[Xe\right]4f^{7}5d^{1}6s^2$.