Question

Which among the following has the highest ionic radius ?

• A. $F^{-}$
• B. $B^{3+}$
• C. $O^{2-}$
• D. $L{i}^{+}$

Answer 1

Answer: (C)

$O^{2-}$

$F^{-}$ and $O^{2-}$ are isoelectronic species possessing 10 electrons each.

$L{i}^{+}$ and $B^{3+}$ are isoelectronic species possessing 2 electrons each.

Since in the case of $O^{2-}$, there is greater electron-electron repulsion and lesser effective nuclear charge, $O^{2-}$ has the largest ionic radius in this case.