Chemistry - f-block Question with Solution | TestHub

Exchange energy is the energy released when two or more electrons with the same spin exchange their positions in the degenerate orbitals of a subshell. On losing third ${\mathrm{e}}^{-}$, Gadolinium achieves half filled $4\mathrm{f}$-orbital configuration, which has higher exchange enthalpy.

$\mathrm{Gd}=\left[\mathrm{Xe}\right] 4{\mathrm{f}}^{7}5{\mathrm{d}}^{1}6{\mathrm{s}}^2$.