Question

Which of the following is the correct order of relative size?

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

Answer 1

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

$I^{-}>I>I^{+}$

$I^{+}$ is formed when one valence electron is removed from the outermost shell of a neutral atom. Removal of electron results in a decrease in $e^{-}$$-e^{-}$ repulsion (shielding decreases) thus leading to a decrease in atomic size.

On the other hand, $I^{-}$ is formed when an extra electron is added to a neutral atom. As an additional electron is added, $e^{-}$-$e^{-}$ repulsion increases (shielding increases) thus pushing the electrons further apart. Also, the protons cannot pull the electrons that tightly now, resulting in a decrease in effective nuclear charge. This leads to an increase in the atomic radius of the anion.

Hence, the correct option is $\text{B}$