Chemistry - f-block Question with Solution | TestHub

Electronic configuration of $\mathrm{Ce} \mathrm{and} \mathrm{Eu}$ in ground state are following:

$$\begin{gathered} \mathrm{Ce}=\left[\mathrm{Xe}\right] 4{\mathrm{f}}^1 5{\mathrm{d}}^1 6{\mathrm{s}}^2 \\ \mathrm{Eu}=\left[\mathrm{Xe}\right] 4{\mathrm{f}}^7 6{\mathrm{s}}^2 \end{gathered}$$

Trivalent cerium means cerium loss three electrons and obtain $+3$ charge and bivalent Europium means Europium loss two electrons and obtain $+2$ charge, so their electronic configurations are following

$\mathrm{E}{\mathrm{u}}^{2+}:\left[\mathrm{X}\mathrm{e}\right]4{\mathrm{f}}^7$

$\mathrm{C}{\mathrm{e}}^{3+}:\left[\mathrm{X}\mathrm{e}\right]4{\mathrm{f}}^1$