What group naturally (without forming ions) has a full outer shell?
Noble gases have a full outer electronic shell (without forming any ions). These elements reside in Group 18 of the periodic table. There are 6 naturally occurring noble gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) and radon (Rn). Given a full outer electronic shell, these elements have a very low tendency to react with other elements and form compounds and thus exhibit very low chemical reactivity. At standard conditions, these elements exist as colorless and odorless gases.
The electronic configuration of some of these noble gases are:
He: atomic number = 2, electronic configuration: 1 s^2
Neon: atomic number: 10, electronic configuration: 1 s^2, 2 s^2, 2 p^6
Argon: atomic number: 18, electronic configuration: 1 s^2, 2 s^2, 2 p^6, 3 s^2, 3 p^6
and so on.
Hope this helps.