Gadolinium belongs to the $4f$ series. Its atomic number is $64$. Which of the following is the correct electronic configuration of gadolinium?

The atomic number of Gadolinium ($\text{Gd}$) is $64$.The noble gas preceding it is Xenon ($\text{Xe}$) with $Z=54$.The general configuration for Lanthanides is $[\text{Xe}]4f^{n}5d^{0-1}6s^2$.For $\text{Gd}$ ($Z=64$):$54+2(\text{in }6s)=56$ electrons.The remaining $8$ electrons are distributed. To achieve a stable half-filled $f$ -orbital ($4f^7$), one electron enters the $5d$ orbital.Thus, the configuration is $[\text{Xe}]4f^{7}5d^{1}6s^2$.