Chemistry - Complete d-block Question with Solution | TestHub

The second series of transition elements is the $4d$ series, which starts from Yttrium ($Z=39$) and ends at Cadmium ($Z=48$).

The noble gas preceding this series is Krypton ($[\text{Kr}]$, $Z=36$).

The valence electrons are filled in the $4d$ and $5s$ subshells. Due to anomalous configurations (for example, Palladium has the configuration $[\text{Kr}]4d^{10}5s^0$ and elements like Silver have $[\text{Kr}]4d^{10}5s^1$), the number of electrons in the $5s$ orbital can be $0$, $1$, or $2$.

Thus, the general electronic configuration of the $2^{\text{nd}}$ transition series is $[\text{Kr}]4d^{1-10}5s^{0-2}$.