Question:
The electronic configurations of bivalent europium and trivalent cerium are:
(atomic number: $\mathrm{Xe}=54, \mathrm{Ce}=58, \mathrm{Eu}=63$ )
Correct Option: , 2
Solution:
$\mathrm{Eu}^{2+}:[\mathrm{Xe}] 4 f^{7} ; \mathrm{Ce}^{3+}:[\mathrm{Xe}] 4 f^{1}$