Which of the following properties is $NOT$ correct for alkali metals?

Comment on each of the following observations:
$(a)$ The mobilities of the alkali metal ions in aqueous solution are $Li^{+} < Na^{+} < K^{+} < Rb^{+} < Cs^{+}$
$(b)$ Lithium is the only alkali metal to form a nitride directly.
$(c)$ The standard electrode potential $E^{\circ}$ for the reaction $M^{2+}_{(aq)} + 2e^{-} \to M_{(s)}$ (where $M = Ca, Sr$ or $Ba$) is nearly constant.

Which of the following alkali metals is smallest in size?

Among alkali metal salts,lithium salts are the least conducting in their aqueous solutions. This is due to:

When potassium is heated strongly in oxygen,it forms:

Thermal decomposition of sodium nitrate at temperatures above $800\,^oC$ yields ..........