How is helium different from neon and argon? How is it similar?
Helium has an outer electron shell of only 2 electrons Neon and Argon have outer shells of 8 electrons all three have filled outer shells and are unusually stable.
The filled outer shells of Group VIIIA or the noble gases makes all me members of this family ( including Helium, Neon and Argon) the most stable of all the elements. These three elements have this property in common, a filled stable outer electron shell.
Helium having the smallest outer electron shell needs only two electrons to fill first shell.
Argon and Neon being in the second and third periods need 8 electrons to fill their outer shells.