The electronic configuration of an element $X$ is $2, 8, 8, 2$. To which $(a)$ period and $(b)$ group of the modern periodic table does $X$ belong? State its valency. Justify your answer in each case.

(N/A) The element $X$ belongs to the $4th$ period because the number of occupied electron shells is $4$.
$(b)$ The element $X$ belongs to the $2nd$ group because it has $2$ valence electrons in its outermost shell.
The valency of element $X$ is $2$ (or $+2$) because it needs to lose $2$ electrons from its outermost shell to achieve a stable noble gas configuration.