Which of the following statements about the Modern Periodic Table is correct?

What is the position of metalloids in the periodic table?

In the Modern Periodic Table,which are the metals among the first ten elements?

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.

$Na, Mg, Al, Si, P, S, Cl$ and $Ar$ are the elements of the third period.
$(a)$ Which one of them is an inert gas? Why?
$(b)$ Which one of them has a valency of $4$? What kind of bond does it form: ionic or covalent?
$(c)$ Which of them are electropositive? Pick any two.

Write two reasons responsible for the late discovery of noble gases.