Halógen

Halogen is a term used to describe a group of chemical elements belonging to Group 17 of the periodic table. These elements are fluorine, chlorine, bromine, iodine, and astatine. They are characterized by their high reactivity and their tendency to form salts with metals, hence the name "halogen" which derives from the Greek words "hals" (salt) and "gen" (to form).

In their elemental state, halogens exist as diatomic molecules, meaning they are composed of two atoms of the same element, such as F2, Cl2, Br2, and I2. Their physical states vary at room temperature: fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Astatine is a radioactive element and its properties are less well-understood due to its scarcity.

Halogens readily gain one electron to achieve a stable electron configuration, making them strong oxidizing agents. This reactivity leads them to form a wide variety of compounds with other elements. For instance, they form ionic salts with alkali metals, like sodium chloride (table salt). They also form covalent compounds with nonmetals, such as hydrogen halides (e.g., HCl).

The properties of halogens change gradually across the group. Electronegativity and oxidizing strength decrease from fluorine to astatine, while atomic and ionic radii increase. Fluorine is the most electronegative element, while astatine is the least reactive among the halogens. These elements and their compounds have numerous applications in industries such as sanitation, medicine, and manufacturing.