Question

Calculate the number of $4\mathrm{f}$ electrons present in ${\mathrm{Gd}}^{+2}$. (Atomic number = $64$)

Answer 1

• Electronic configuration of $\mathrm{Gd}$$=\left[\mathrm{Xe}\right]4{\mathrm{f}}^{7}5{\mathrm{d}}^{1}6{\mathrm{s}}^2$
• Electronic configuration of ${\mathrm{Gd}}^{+2}$ $=\left[\mathrm{Xe}\right]4{\mathrm{f}}^{7}5{\mathrm{d}}^1$
• Due to orbital contraction, the electron of 5d will get transferred into 4f and its electronic configuration will be ${\mathrm{Gd}}^{+2}=\left[\mathrm{Xe}\right]4{\mathrm{f}}^{8}5{\mathrm{d}}^0$

Hence, the number of $4\mathrm{f}$ electrons present is ${\mathrm{Gd}}^{+2}=8$