Question

Which of the following ions has the highest value of ionic radius?

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

Answer 1

The correct option is C $O^{2-}$

$O^{2-}$ has the highest value of ionic radius.
$O^{2-}$ has lower nuclear charge than isoelectronic $F^{-}$.

Hence, the valence electrons in $O^{2-}$ are loosely held than in $F^{-}$. Due to this, the ionic radius of $O^{2-}$ is greater than that of $F^{-}$. Isoelectronic $L{i}^{+}$ and $B^{3+}$ contain one electron shell less than $O^{2-}$ and $F^{-}$.

Hence, valence electrons in $L{i}^{+}$ and $B^{3+}$ are tightly held than in $O^{2-}$. Due to this the ionic radius of $O^{2-}$ is greater than that of $L{i}^{+}$ and $B^{3+}$