Question
Chemistry Question on d -and f -Block Elements
The electronic configuration of gadolinium (at. no. = 64) is
A
[Xe]4f35d56s2
B
[Xe]4f65d26d2
C
[Xe]4f85d96s2
D
[Xe]4f75d16s2
Answer
[Xe]4f75d16s2
Explanation
Solution
The electronic configuration of La(Z=57) is [Xe]5d16s2. Therefore, further addition of electrons occurs in a lower energy 4f -orbital till it is exactly half filled at Eu(Z=63). Thus, the electronic configuration of Eu is [Xe]4f76s2. Therefore, addition of next electron doesn't occur in a more stable exactly half-filled 4f7 shell but occur in a little higher energy 5d-orbital. Thus, the electronic configuration of Gd(Z=64) is [Xe]4f75d16s2