[પરમામાણ્વીય ક્રમાંક ${Gd}=64$ ]
\({ }_{64} {Gd}:[{Xe}] 4 {f}^{7} 5 {~d}^{1} 6 {~s}^{2}\)
So the electronic configuration of
\({ }_{64} {Gd}^{2+}:[{Xe}] 4 {f}^{7} 5 {~d}^{1} 6 {~s}^{0}\)
\(i.e.\) the number of \(4 {f}\) electrons in the ground state electronic configuration of \({Gd}^{2+}\) is \(7\)
$(1)\,Cu^{2+}$ $(2)\,Ti^{4+}$ $(3)\, Co^{2+}$ $(4)\,Fe^{4+}$