Notes

The Reasons of Helium in Rare Gases…

The most important reason for helium is this:
(i) Helium is slightly different than the other noble gas elements. It only has two electrons in its outer shell.
(ii) All group members except helium have eight valence electrons.
(iii) Helium is an element with a very low boiling point.
(iv) Helium is chemically inert, transfers heat readily, and does not become radioactive.
(v) Helium is non-flammable; 93% lifting power as compare to flammable hydrogen.
(vi) Helium is an element non-flammable, non-reactive.