Question

Explain why cations are smaller and anions are larger than their parent atom.

Answer 1

Cations are always smaller than their parent atoms because

• They are formed by losing electrons, due to which they have lesser electrons, while their nuclear charge remains the same.
• So, the remaining electrons are therefore held more tightly by the protons in the nucleus
• Thus their ionic radii are smaller than the parent atoms.

Anions are always larger than their parent atoms because

• They are formed by gaining electrons, and the addition of 1 or more electrons results in increased repulsion among the electrons and a decrease in the effective nuclear charge.
• So, the electrons are loosely held by the protons in the nucleus.
• Thus their ionic radii are greater than the parent atoms.