Which of the following sequences is the correct order of the size of species?
Which of the following sequences is the correct order of the size of species?
$\mid>I^{+}>I^{-}$
$\mathrm{I}^{-}>\mathrm{I}^{+}>\mathrm{I}^{-}$
$1^{+}>I^{-}>I^{-}$
$I^{-}>I^{\prime}>I^{+}$
Solution
For a particular element, the order of size of anion, cation and neutral species is anion > element $>$ cation.
Cation has smallest size due to greater $\left(Z_{\text {eff }}\right)$ effective nuclear charge.
Size is inversely proportional to $Z_{\text {eff }}$, which is directly proportional to positive charge.
Thus, $\mathrm{I}^{-}>\mathrm{I}>\mathrm{I}^{+}$.