Question

Why size of action is note than its parent atom

Answer 1

Pls check its cation not action

Cations are always smaller than their parent atoms this is because they have lesser electrons, while their nuclear charge remains the same. 

Answer 2

An anion, a negatively charged ion, has more electron(s) than in its neutral atom state (for example Cl-). Since it has more electrons, but the same number of protons, the electrons “feel” a weaker force of attraction from the positively charged nucleus. There is also more electrostatic repulsion between the negatively charged electrons, which means that the electrons push each other away more strongly. The combination of these two factors expands the electron cloud of the atom, making its atomic radius. So, the new, resulting anion is bigger than its parent atom