Question

The size of the species $I,I^{-}$ & $I^{+}$ follows the order:

• A. $I>I^{-}>I^{+}$
• B. $I^{+}>I>I^{-}$
• C. $I^{-}>I>I^{+}$
• D. $I^{+}>I^{-}>I$

Answer 1

The correct option is C $I^{-}>I>I^{+}$

If we have an element X and the species $X^{+}$ and $X^{-}$, the trend in size generally followed is: $X^{-}>X>X^{+}$.

This is because the anion will have an extra electron to accommodate while the magnitude for nuclear charge remains the same making the size of the ion to be bigger than the neutral atom.
On the other hand, the cation is generally smaller as the number of protons increases due to which there is an increase in the effective nuclear charge, so attraction forces increase so radius decreases.