Where would you locate the element with electronic configuration $2, 8$ in the Modern Periodic Table?

An element which is an essential constituent of all organic compounds belongs to

The elements $Be$,$Mg$,and $Ca$,each having two electrons in their outermost shells,are in periods $2$,$3$,and $4$ respectively of the modern periodic table. Answer the following questions,giving justification in each case:
$(i)$ Write the group to which these elements belong.
$(ii)$ Name the least reactive element.
$(iii)$ Name the element having the largest atomic radius.

It was assumed by Newlands that only :

Four elements $P, Q, R$ and $S$ have atomic numbers $12, 13, 14$ and $15$ respectively.
Answer the following questions giving reasons:
$(i)$ What is the valency of $Q$?
$(ii)$ Classify these elements as metals and non-metals.
$(iii)$ Which of these elements will form the most basic oxide?

Find the atomic number of the element whose electronic configuration is $2, 8, 5$.