Question

why cations are smaller and anions are larger than their parent atoms ?​

Answer 1

The effective nuclear charge is more in cation and less in anion when compared to parent atom.

Size of atom (or) α (ion) α 1/ effective nuclear charge

so the size of cation is smaller and anion is larger when compared to neutral atom.

Answer 2

Explanation:

Cations are always smaller than their parent atoms this is because they have lesser electrons, while their nuclear charge remains the same. The remaining electrons are, therefore held more tightly by the protons in the nucleus and thus their radii.are smaller than the parent atoms. This is opposite in case of anions. Anions are always larger than their parent atomsbecause the addition of 1 or more electrons would result in increased repulsion among the electrons and a decrease in the effective nuclear charge