The electronic configuration of gadolinium (atomic number 64) is:

Options

A. `[Xe] 4f^(3) 5d^(5) 6s^(2)`
B. `[Xe]4f^(7) 5d^(2) 6s^(1)`
C. `[Xe] 4f^(7) 5d^(1) 6s^(2)`
D. `[Xe]4f^(8) 5d^(6) 6s^(2)`

Answer

C

Explanation

The electronic configuration of La (Z= 57) is `[Xe ] 5d^(1) 6s^(2) ` ( refer to footnote on gage `(3//14)` Therefore further addition of electron occurs in the lower energy 4f- orbital till it is exactly half - filled at Eu (Z= 63 ) . Thus the electronic configuration of `[Xe] 4f^(7) 6s^(2)`, Thereafter addition of next electron does not occur in the more stable exactly half-filled `4f^(7)` shell but occurs in the little higher energy 5d- orbital Thus , the electronic configuration of Gd (Z= 64) is `[Xe] 4f^(7) 5d^(1) 6s^(2)` i.e., option ( c) is correct.