The solubility of metal halides depends on their nature,lattice enthalpy and hydration enthalpy of the individual ions. Amongst fluorides of alkali metals,the lowest solubility of $LiF$ in water is due to

Why does lithium differ from other alkali metals?

Chemically,philosopher's wool is

Give the uses of alkali metal elements (group-$I$).

When substance $A$ reacts with water,it produces a combustible gas $B$ and a solution of substance $C$ in water. When another substance $D$ reacts with solution $C$,it produces the same gas $B$,even when reacting with dilute sulfuric acid at room temperature. $A$ gives a golden yellow flame in a Bunsen burner flame. What are $A, B, C,$ and $D$ respectively?

Explain the trend of ionisation enthalpy of alkali metals as we move from top to bottom in the group.