Which of the following compounds is formed when sodium burns in excess supply of air?

$A$ $\xrightarrow{\Delta} B + C_{(gas)}$ $\xrightarrow{Ca(OH)_2} D_{(milky)} + H_2O$ $\xrightarrow{C_{(gas)}} E$. Then the incorrect statement is:

Ionic mobility of which of the following alkali metal ions is lowest when aqueous solution of their salts are put under an electric field?

Which of the following metals reacts directly with nitrogen to form a nitride?

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 significance of sodium,potassium,magnesium,and calcium in biological fluids.