The elements of group eighteen of the periodic table are given
(i) The elements of this group are unreactive, why ?
(ii) Which atom is bigger in size Ne or Ar, Why?

Explanation

(i) The elements of group 18 (also called noble gas elements) are unreactive since they have two valence electrons in the element He and eight in rest of the elements. This means that these elements have complete valence shells. Therefore, these are unreactive chemically.
(ii) Both Ne and Ar belong to group 18. The element Ar is placed below Ne. Since atomic size increases down the group, the element Ar is bigger in size.