question_answer

The atomic radii of alkali metals (M) 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\[Rb)\]? [MP PMT 1997]

A) Gradual increase in ionisation energy

B) Increasing weakness of the metallic bond

C) Increasing electropositive character

D) Decreasing degree of hydration