Helium has an atomic number of two so for its outer energy level is full. Helium is considered

Helium is considered as noble gas or inert gas because it belongs to noble family in the periodic table.

Explanation:

Helium is stable atom because it has complete outermost shell i. e. 2 electrons. Except noble gases, all the elements are reactive because they have incomplete outermost shell so for attaining stability, they form bonds with each other and attain the electronic configuration of noble gases. Helium has given the name of noble gas due to stability.