# Which one of the following is the smallest in size ?

$(a)\;N^+ \\(b)\;F^- \\ (c)\;N^{3-} \\ (d)\;O^{2-}$

$N^{+}$ is the smallest in size.
Number of electrons are same in all but nuclear charge is maximum in $Na^+$. Hence it is the smallest
Hence a is the correct answer.
edited Nov 25, 2017