Question

Consider the following statements :
(I) $C{s}^{+}$ ion is more highly hydrated than other alkali metal ions.
(II) Among the alkali metals $Li,Na,K,$ and $Rb,Li$ has the higher melting point.
(III) Among the alkali metals, only $Li$ forms a stable nitride by direct combination.

• A. (I) and (III) are correct.
• B. (II) and (III) are correct
• C. (I), (II), and (Ill) are correct
• D. (I) and (II) are correct

Answer 1

The correct option is B (II) and (III) are correct

Option (B) is correct.

(I).$L{i}^{+}$ ion is more highly hydrated than other alkali metal ions.

Lithium is the smallest in size among the alkali metals. Hence, $L{i}^{+}$ ion can polarize water molecules more easily than other alkali metals. As a result, water molecules get attached to lithium salts as water of crystallization.

(II). Among the alkali metals $Li,Na,K$ and $Rb$, $Li$ has the higher melting point.

The melting point decreases on going down the group from $Li$ to $Cs$, as the charge density decreases because of the increase in size of monovalent cation.

(III). Among the alkali metals, only $Li$ forms a stable nitride by direct combination.

This is due to small size and greater polarizing power of lithium.Its reducing power and electrode potential are also high.