Question

Consider the following elements :

${}_{20}Ca{,}_{8}O,{}_{18}Ar,{}_{16}S,{}_{4}Be,{}_{2}He$

Which of the above elements would you expect to be :

(i) very stable? (ii) in group 2 of the periodic table?

(iii) in group 16 of the periodic table ?

Answer 1

(i) ${}_{18}Ar$ and ${}_{2}He$ are very stable elements, as their valence shells are completely filled. They belong to the group of inert or noble gases.

(ii) ${}_{20}Ca$ and ${}_{4}Be$ are the two elements that belong to group 2 of the periodic table. This is because their valency is 2 and they are electropositive.

(iii) ${}_{8}O(2,6)$ and ${}_{16}S(2,8,6)$ are the two elements that belong to group 16 of the periodic table.

Group number = Valence shell + 10
= 6 + 10 = 16