Final answer:
The halogens in Group 17 on the periodic table consist of fluorine, chlorine, bromine, iodine, and astatine. These highly reactive nonmetals form important compounds with metals and are found in nature mostly as halide ions. They also play vital roles in biological functions, such as iodine for thyroid health.
Step-by-step explanation:
The halogens are a group of elements located in Group 17 on the periodic table. These elements include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). They are characterized as highly reactive nonmetals, with each showing different states at room temperature; chlorine is a gas, bromine a liquid, and iodine a solid. The halogens react readily with metals to form a wide range of compounds, such as sodium chloride and calcium chloride.
Halogens exist naturally in various forms, including diatomic molecules like F₂, Cl₂, Br₂, and I₂. Given their reactivity, they don't occur freely in nature but are commonly found as halide ions in seawater, minerals, and other compounds. These elements are crucial for various applications, including roles in bodily functions such as the iodine needed by the thyroid gland and chlorine present as hydrochloric acid in stomach acid.