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

$Na, Mg, Al, Si, P, S, Cl$ 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.

State whether the following statement is true or false: In $1913$,Dmitri Ivanovich Mendeleev showed that the atomic number of an element is a more fundamental property than its atomic mass.

$(a)$ Predict which of the following will form anions and which will form cations:
$(i)$ $Na$ $(ii)$ $Al$ $(iii)$ $Cl$ $(iv)$ $O$
$(b)$ Name two elements that are inert.

Write true or false for the statement: Electronic configuration of hydrogen resembles that of alkaline earth metals.

Why are lithium (atomic number $3$) and potassium (atomic number $19$) placed in group $1$? What will be the atomic numbers of the first two elements in group $2$?