halogenanions

Halogenanions are negatively charged ions formed from halogen elements. The halogens are fluorine, chlorine, bromine, iodine, and astatine, located in Group 17 of the periodic table. When a halogen atom gains one electron, it achieves a stable electron configuration, resembling that of the following noble gas. This results in the formation of a halide ion, with a charge of -1. For example, a fluorine atom (F) gains an electron to become a fluoride ion (F⁻), chlorine (Cl) becomes chloride (Cl⁻), bromine (Br) becomes bromide (Br⁻), and iodine (I) becomes iodide (I⁻). Astatine, being radioactive, also forms the astatide ion (At⁻).

These halide ions are common in chemistry and play vital roles in various compounds and processes. They are typically found in ionic salts, such as sodium chloride (NaCl), potassium bromide (KBr), and calcium fluoride (CaF₂). In aqueous solutions, they act as common anions and participate in many chemical reactions. The size and charge density of halide ions vary down the group, influencing their properties and reactivity. For instance, fluoride is the smallest and most electronegative, while iodide is the largest and least electronegative among the stable halogens. Their presence is essential in biological systems, industrial processes, and environmental chemistry.