Question: The electronic configurations of bivalent europium and trivalent cerium are
(atomic number: $\mathrm{Xe}=54, \mathrm{Ce}=58, \mathrm{Eu}=63$ )
$[\mathrm{Xe}] 4 \mathrm{f}^{4}$ and $[\mathrm{Xe}] 4 \mathrm{f}^{9}$
[Xe] $4 \mathrm{f}^{7}$ and [Xe] $4 \mathrm{f}^{1}$
$[\mathrm{Xe}] 4 \mathrm{f}^{7} 6 \mathrm{~s}^{2}$ and $[\mathrm{Xe}] 4 \mathrm{f}^{2} 6 \mathrm{~s}^{2}$
$[\mathrm{Xe}] 4 \mathrm{f}^{2}$ and [Xe] $4 \mathrm{f}^{7}$
Correct Option: , 2
Solution:
