MCQ
The electronic configuration of Gadolinium is
- A$[Xe]6s^2\,\,4f^8$
- B$[Xe] 6s^2\,\, 5d^1\,\, 4f^8$
- ✓$[Xe] 6s^2\,\,5d^1\,\,4f ^7$
- DNone
✓
Answer
Correct option: C.
$[Xe] 6s^2\,\,5d^1\,\,4f ^7$
c
The electronic configuration of $La ( Z =57)$ is $[ Xe ] 5 d ^1 6 s ^2$. Therefore, further addition of electrons occurs in a lower energy $4 f$-orbital till it is exactly half filled at $Eu ( Z =63)$. Thus, the electronic configuration of $Eu$ is $[ Xe ] 4 f ^7 6 s ^2$. Therefore, addition of next electron doesn't occur in a more stable exactly halffilled $4 f ^7$ shell but occur in a little higher energy $5 d$-orbital. Thus, the electronic configuration of $Gd ( Z =64)$ is $[ Xe ] 4 f ^7 5 d ^1 6 s ^2$.
The electronic configuration of $La ( Z =57)$ is $[ Xe ] 5 d ^1 6 s ^2$. Therefore, further addition of electrons occurs in a lower energy $4 f$-orbital till it is exactly half filled at $Eu ( Z =63)$. Thus, the electronic configuration of $Eu$ is $[ Xe ] 4 f ^7 6 s ^2$. Therefore, addition of next electron doesn't occur in a more stable exactly halffilled $4 f ^7$ shell but occur in a little higher energy $5 d$-orbital. Thus, the electronic configuration of $Gd ( Z =64)$ is $[ Xe ] 4 f ^7 5 d ^1 6 s ^2$.
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