The electronic configurations of Eu (Atomic No.63), Gd (Atomic No.64 and Tb (Atomic No.65) are :

The electronic configurations of Lanthanide elements Eu (Z = 63) , Gd (Z = 64) and Tb (Z = 65) are given in the below.

Eu(AtomicNo.63)$\to \left[\mathrm{Xe}\right]4{\mathrm{s}}^{7}6{\mathrm{s}}^2$

Cd(AtomicNo.64) →$\left[\mathrm{Xe}\right]4f^{7}5d^{1}6s^2$

Tb(AtomicNo.65) →$\left[\mathrm{Xe}\right]4f^{9}6s^2$