In terms of reactivity, which group is known for being nonreactive?

The noble gases are known for their nonreactivity due to their complete valence electron configuration. Each noble gas has a full outer shell, which means they do not tend to gain, lose, or share electrons with other elements. This stable configuration allows them to exist without forming compounds under normal conditions, making them largely inert.

In contrast, alkali metals, alkaline earth metals, and halogens are characterized by their high reactivity. Alkali metals have one electron in their outer shell, making them eager to lose that electron in reactions. Alkaline earth metals have two outer electrons and readily lose them. Halogens, with seven valence electrons, tend to gain an electron to achieve stability. This striking difference in electron configuration and resulting chemical behavior underscores why noble gases are classified as nonreactive.