Write any two uses of helium.
 

 Write any two uses of the following:

Neon

Complete the following chemical equation:

${\mathrm{XeF}}_2 + {\mathrm{PF}}_5 \stackrel{ }{\to }$

Complete the following chemical equations:

${\mathrm{PCl}}_{5 }+ {\mathrm{H}}_2\mathrm{O} \left(\mathrm{excess}\right) \stackrel{ }{\to }$
 

Give reason for the difference in the following:

 Stabilities of $+3$ oxidation state of $\mathrm{P}$ and $\mathrm{Bi}$.