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

The group known for being highly reactive nonmetals is the halogens. This group includes elements like fluorine, chlorine, bromine, iodine, and astatine. Halogens have seven valence electrons, which makes them eager to gain one more electron to achieve a stable octet configuration, resulting in high reactivity, particularly with alkali metals and alkaline earth metals. This reactivity is a defining characteristic of halogens.

In contrast, alkali metals are highly reactive but fall under the category of metals, not nonmetals. Noble gases, on the other hand, are known for their lack of reactivity due to having a full valence shell, making them very stable and not prone to forming bonds under normal conditions. Transition metals exhibit varied properties and reactivities but are primarily classified as metals rather than nonmetals. Therefore, the halogens stand out as the group of highly reactive nonmetals.