WHY HELIUM MOLECULE IS NOT FOUND ?

MO DIAGRAM OF HYDROGEN, HELIUM & CARBON MOLECULE

Why Helium is totally inert ?

At what temperature the rms velocity of helium molecules will be equal to that of hydrogen molecules at NTP ?

What will be the root mean square speed of helium at 40^(@) C , if mean square speed of oxygen molecule at 0^(@) C is 460 m//s ? Molecule weight of oxygen is 32 g//"mole" and of helium is 4 g//"mole" .

Molecular hydrogen at one atmosphere and helium at two atmosphere occupy volume V each at the same temperature. The rms velocity of hydrogen molecules is x times the rms velocity of helium molecules. What is the value of x ?

Why is helium used in diving apparatus?