Why alkali metals has lower boiling points than that of alkaline earth metals?

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R:

Assertion A: Metallic sodium dissolves in liquid ammonia giving a deep blue solution, which is paramagnetic.
Reasons R: The deep blue solution is due to the formation of amide.

In the light of the above statements, choose the correct answer from the options given below:

The correct order of hydration enthalpies is

(A) ${\mathrm{K}}^{+}$
(B) ${\mathrm{Rb}}^{+}$
(C) ${\mathrm{Mg}}^{2+}$
(D) ${\mathrm{Cs}}^{+}$
(E) ${\mathrm{Ca}}^{2+}$

Choose the correct answer from the options given below:

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Lithium salts are hydrated.
Reason (R) : Lithium has higher polarising power than other alkali metal group members.

In the light of the above statements, choose the most appropriate answer from the options given below :

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason $\mathrm{R}$. Assertion $\mathrm{A}$ : $\mathrm{LiF}$ is sparingly soluble in water. Reason $\mathrm{R}$ : The ionic radius of ${\mathrm{Li}}^{+}$ ion is smallest among its group members, hence has least hydration enthalpy.

In the light of the above statements, choose the most appropriate answer from the options given below.

The mobilities of alkali metal ions in aqueous solution are: ${\text{Li}}^{+}<{\text{Na}}^{+}<{\text{K}}^{+}<{\text{Rb}}^{+}<{\text{Cs}}^{+}$.