(i) The elements which belong to the group called the noble gases are considered to be inert elements. These elements are so-called ‘inert’ because of their reluctance to take part in the chemical reactions. This nature is exhibited mostly by the noble gases because very few of the noble gases take part in the chemical reaction.

(ii) The valency of the inert elements is zero. As most of the inert elements are noble gases they have atomic numbers in which their valence shell is completely filled. Examples are Neon and Argon they have fully filled octet in their outermost shell due to which the valency of the elements is zero.

(iii) The general formula for the maximum number of electrons in any shell is 2(n²) where ‘n’ is the number of the shell, like n = 1, 2, 3…… for shells K, L, M, N…….

For M and N shells n = 3 and 4 respectively. So the maximum electrons using the formula are 18 and 32. But is difficult for an atom to hold more than 8 electrons in any shell because of the repulsion forces between electrons which affect the stability of the atom.

So only 8 electrons can be accommodated in M and N shells.