Question

Among the alkali metals, which element has

(a) Strongest reducing character in aqueous medium

(b) lowest size of ion in aqueous medium.

Answer 1

Among alkali metals,
a) Strongest reducing agent in aqueous medium: Lithium
Reason: Due to small size of lithium ion it gets more hydrated and thus have more hydration energy which compensates the high ionisation energy of lithium.
b) Lowest size of the ion in aqueous medium: Cesium
Reason: In aqueous medium, alkali metal ions are highly hydrated. Smaller the ion more is the degree of hydration which results in bigger size of the ion. Hence the ionic radii in aqueous medium follows the order Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺