The number of molecules from the following which contain only two lone pair of electrons is ________

$$\mathrm{H}_{2} \mathrm{O}, \mathrm{N}_{2}, \mathrm{CO}, \mathrm{XeF}_{4}, \mathrm{NH}_{3}, \mathrm{NO}, \mathrm{CO}_{2}, \mathrm{~F}_{2}$$

For a metal ion, the calculated magnetic moment is $$4.90 ~\mathrm{BM}$$. This metal ion has ___________ number of unpaired electrons.

In alkaline medium, the reduction of permanganate anion involves a gain of __________ electrons.

The difference in the oxidation state of $$\mathrm{Xe}$$ between the oxidised product of $$\mathrm{Xe}$$ formed on complete hydrolysis of $$\mathrm{XeF}_{4}$$ is ___________