Which of the following groups contains very stable elements with full outer electron shells?

The group that contains very stable elements with full outer electron shells is the noble gases. These elements are found in Group 18 of the periodic table. What sets noble gases apart is their electron configuration; they have complete valence electron shells, which typically consists of eight electrons. This stable configuration makes them highly unreactive, as they do not easily gain or lose electrons to form bonds with other elements.

In contrast, the other groups listed do not possess this characteristic. Transition elements, while often stable, have partially filled electron shells and exhibit a variety of oxidation states, making them more reactive than noble gases. Halogens, found in Group 17, are very reactive because they have seven electrons in their outer shell and readily gain an electron to achieve stability. Alkali metals, located in Group 1, have a single electron in their outer shell and are highly reactive, as they tend to lose that electron to attain a full outer shell.

Thus, the noble gases are unique in their full outer electron shells and correspondingly low reactivity, making them the group that embodies stability among the elements.