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

$\begin{array}{1 1}(a)\;N_3^-&(b)\; O_2^-\\(c)\;F^-&(d)\;Na^+\end{array}$

$Na^+$ is the smallest in size among the $N^{3-},F^-,O^{2-}$ and $Na^{+}$
Hence (d) is the correct answer.
answered Mar 5, 2014