Question

Which one of the following is the smallest in size

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

Answer 1

Answer: (D)

$Na^{+}$

Answer 2

$Na^{+} < F^{-} < O^{2 -} < N^{3 -}$

All are isoelectronic, effective number charge is highest for $Na^{+}$ so it has smallest size.