Question

Consider the following ions

. The largest cation and largest anion are respectively}

• A. $Cs^{+}, S^{2-}$
• B. $Cs^{+}, P^{3-}$
• C. $Ba^{2+}, Cl^{-}$
• D. $K^{+}, P^{3-}$

Hint:

For isoelectronic ions: \[ \text{Radius} \propto \frac{1}{Z} \] Lower nuclear charge means larger ionic radius.

Answer 1

The Correct Option is B

Concept: Ionic size increases down a group. For isoelectronic species, radius decreases as nuclear charge increases.

Step 1: Identify the largest cation.
Among \[ Mg^{2+},\ Ca^{2+},\ K^{+},\ Ba^{2+},\ Cs^{+} \] size increases down the group. Therefore, \[ Cs^{+} \] is the largest cation.

Step 2: Identify the largest anion.
Among \[ P^{3-},\ S^{2-},\ Cl^{-} \] all are isoelectronic. The species with the smallest nuclear charge has the largest radius. \[ P^{3-} \] has the smallest nuclear charge. Hence it is the largest anion. \[ \boxed{Cs^{+},\ P^{3-}} \]