Question

On moving down the group, the radius of an ion
a) Decreases
b) Increases
c) No change
d) None of these

Answer 1

On moving down the group, the radius of an ion -- Increases.

Explanation :

An atom with a charge is called as An Ion.
If a neutral atom looses electron it is called as cation and if neutral atom gains electrons it is called as Anion. 

In a group, radius of an ion increases because the size of the atom increases down the group..
As we move down in a group the additional electron is added to new shell .Hence increase in its radius