WAEC - Chemistry (2017 - No. 4)
The species with no electron in the 3d-orbital is
\(Zn^{2+}\)
\(Sc^{3+}\)
Cu
\(Mn\)
Explication
Scandium has electronic configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{1}4s^{2}\) hence, \(Sc^{3+}\) has configuration \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}\). Hence, no electron in the 3d-orbital.