Give the uses of helium .

Explanation

(i) Helium and oxygen mixture is used by divers in place of air oxygen mixture. This prevents the painful dangerous condition called bends.
(ii) Helium is used to provide inert atmosphere in electric are welding of metals.
(iii) Helium has lowest boilings point hence used in cryogenics ( low temperature science).
(iv) It is much less denser than air and hence used for filling air balloons .