Question

The atomic radii of alkali metals $\left(M\right)$ lie in the order $Li<Na<K<Rb$ but the radii of $M^{+}$ ions in aqueous solution lie in the reverse order $L{i}^{+}>N{a}^{+}>K^{+}>R{b}^{+}$. What is the reason for this reverse order (on going from $Li$ to $Rb$)?

• A. Gradual increase in ionisation energy
• B. Increasing weakness of the metallic bond
• C. Increasing electropostive character
• D. Decreasing degree of hydration

Answer 1

Answer: (D)

Decreasing degree of hydration

Higher the charge density more is the hydration. The charge density of Li ion is highest so its size of hydrated ion will be largest.