Question

The electronic configuration of gadolinium is:

• A. $\left[Xe\right]{4f}^3{5d}^5{6s}^2$
• B. $\left[Xe\right]{4f}^6{5d}^2{6s}^2$
• C. $\left[Xe\right]{4f}^8{5d}^9{6s}^2$
• D. $\left[Xe\right]{4f}^7{5d}^1{6s}^2$

Answer 1

Answer: (D)

$\left[Xe\right]{4f}^7{5d}^1{6s}^2$

Gadolinium, Z= 64

Electronic configuration

Expected : $\left[Xe\right]4f^{8}6s^2$

Observed : $\left[Xe\right]4f^{7}5d^{1}6s^2$

Half filled f orbital is more stable than partially filled f orbital and since energy difference is not much between 4f orbital and 5d orbital thus 1 electron from 4f orbital(expected to have 8e) jumps to 5d orbital making it $5d^1$ thus deviating from the expected configuration and conferring stability through Hund's rule of maximum multiplicity.