Question

The number of $4f$ electrons in the ground state electronic configuration of $G{d}^{2+}$ is_ _______
[Atomic number of $Gd=64$ ]

Answer 1

Answer: 7

The electronic configuration of
${}_{64}Gd:[Xe]4f^{7}5d^{1}6s^2$
So the electronic configuration of
${}_{64}G{d}^{2+}:[Xe]4f^{7}5d^{1}6s^0$
i.e. the number of $4f$ electrons in the ground state electronic configuration of $G{d}^{2+}$ is $7$ .