• # question_answer Ionic radii are   [CBSE PMT 2003, 04] A) Directly proportional to effective nuclear charge B) Directly proportional to square of effective nuclear charge C) Inversely proportional to effective nuclear charge D) Inversely proportional to square of effective nuclear charge.

Ionic radius in the nth orbit is given by ${{r}_{n}}=\frac{{{n}^{2}}a}{z}$ or ${{r}_{n}}\propto \frac{1}{Z}$ where n is principal equation no., ao. bohr's radius of hydrogen atom and Z is the effective nuclear energy.