The element with outer electronic configuration ( n - 1 ) d 2 n s 2 , where n = 4 , would belong to

We know that the general configuration of $\mathrm{d}-$block element is $(\mathrm{n}-1){\mathrm{d}}^{1-10}{\mathrm{ns}}^{1-2}$ where $\mathrm{n}$ is the period number.

Here given electronic configuration is $(\mathrm{n}-1){\mathrm{d}}^2{\mathrm{ns}}^2$, where $\mathrm{n}=4$. So, here the period number will be $4$.

For $\mathrm{d}-$block elements the group number can be found by adding no of electrons in $\left(\mathrm{n}-1\right)\mathrm{d}$ sub-shell and the no of electrons present in the $\mathrm{ns}$ sub-shell.

So, here group number will be $2+2=4$.

Hence, the element belongs to  $4^{\text{th }}$ period and $4^{\text{th }}$ group