Which group of elements is known for being highly reactive nonmetals?

The group of elements known for being highly reactive nonmetals is the Halogens. This group includes fluorine, chlorine, bromine, iodine, and astatine. Halogens are characterized by their need to gain just one additional electron to achieve a stable electron configuration, typically resembling that of the noble gases. This drive to attain a full valence shell makes them highly reactive, especially with alkali and alkaline earth metals, which can readily donate electrons.

The high reactivity of halogens is evident in their vigorous reactions, such as with hydrogen to form hydrogen halides, which are strong acids. For example, when chlorine gas reacts with sodium, it forms sodium chloride (table salt), a quintessential example of halogen reactivity.

In contrast, other groups mentioned do not exhibit this level of reactivity. Noble gases are generally inert due to their complete valence shell. Transition metals, while they can be reactive, exhibit properties of metals rather than nonmetals and have varying levels of reactivity. Alkaline earth metals, also metals, tend to lose two electrons becoming more reactive with water and acids compared to their nonmetal counterparts. Therefore, halogens are distinctly recognized for their high reactivity among nonmetals.