Question

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

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

Answer 1

Answer: (B)

All the ions belongs to same period thus for them cations will be smaller than anions as during cation formation outer orbit is lost and effective nuclear charge increases so size decreases.
$O^{2 -}$ and $F^{-}$ are isoelectronic and $r_{n} \propto \frac{1}{Z}$
So ionic radius of
$O^{2 -}\left(Z = 8\right)>F^{-}\left(Z = 9\right)>Li^{+}\left(Z = 3\right)>B^{3 +}\left(Z = 5\right)$