Question

Why is the radius of the $S^{2-}$ ion $184$ pm while the radius of the $C{l}^{-}$ ion is $181$ pm?

• A. $S^{2-}$ has more electrons shielding the pull from the nucleus compared to $C{l}^{-}$.
• B. $S^{2-}$ has more electrons than $C{l}^{-}$.
• C. $C{l}^{-}$ has a greater effective nuclear charge than $S^{2-}$.
• D. The additional electrons in $S^{2-}$ add another shell to the ion.

Answer 1

The correct option is C $C{l}^{-}$ has a greater effective nuclear charge than $S^{2-}$.

$S^{2-}$ and ${Cl}^{-}$ have equal number of electrons, but ${Cl}^{-}$ has higher effective nuclear charge hence there is more force attracting electrons in ${Cl}^{-}$ hence ${Cl}^{-}$ is smaller. Thus correct answer is option B.