Question

The outer electron configuration of $Gd$. (Atomic number $64$):

• A. $4f^{3}5d^{5}6s^2$
• B. $4f^{8}5d^{0}6s^2$
• C. $4f^{4}5d^{4}6s^2$
• D. $4f^{7}5d^{1}6s^2$

Answer 1

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

Electronic configuration is : $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^{6}5s^{2}4d^{10}5p^{6}6s^{2}4f^{7}5d^1.$

Therefore, outer electronic configuration : $\left[Xe\right]4f^{7}5d^{1}6s^2$.