MCQ
The electronic configuration of gadolinium (atomic no. $64$) is
- A$[Xe]4{f^8}5{d^9}6{s^2}$
- ✓$[Xe]4{f^7}5{d^1}6{s^2}$
- C$[Xe]4{f^3}5{d^5}6{s^2}$
- D$[Xe]4{f^6}5{d^2}6{s^2}$
Therefore, further addition of electrons occurs in the lower energy $4 f$ - orbital till it is exactly half filled at $Eu \,(Z=63)$
Thus, the electronic configuration of $Eu$ is $[ Xe ] \,4 f ^7 \,6 s ^2$, thereafter, addition of next electron does not occur in the more stable exactly half filled $4 f^7$ shell but occurs in the little higher energy $5 d$ - orbital.
Thus, the electronic configuration of $Gd (Z=64)$ is $[X e]\, 4 f^7\, 5 d^1\, 6 s^2$
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
[Given : Specific heat of water $=4.18\, \mathrm{~J} \,\mathrm{~g}^{-1}\, \mathrm{~K}^{-1}$
Density of water $=1.00\, \mathrm{~g}\, \mathrm{~cm}^{-3}$ ]
(Assume no volume change on mixing)