halogenanion

A halogenanion is an anion formed from a halogen atom. Halogens are elements in Group 17 of the periodic table, including fluorine, chlorine, bromine, iodine, and astatine. These elements readily gain one electron to achieve a stable electron configuration, resulting in a negatively charged ion. The most common halogenanions are fluoride (F⁻), chloride (Cl⁻), bromide (Br⁻), and iodide (I⁻). Astatine can also form an astatide anion (At⁻), though it is less common due to the element's radioactivity and rarity.

Halogenanions are typically formed when a halogen atom reacts with a more electropositive element, such as a metal or a metalloid. For instance, when sodium (Na) reacts with chlorine (Cl), sodium chloride (NaCl) is formed, which consists of sodium cations (Na⁺) and chloride anions (Cl⁻). These anions are significant in various chemical processes and are found in numerous ionic compounds. Their properties, such as size and charge density, vary depending on the specific halogen. For example, fluoride is the smallest and most electronegative, while iodide is the largest and least electronegative among the common halogenanions. These differences influence their reactivity and the stability of the compounds they form.