hydroksidiioni

Hydroksidiioni (hydroxide ion; OH−) is an inorganic anion consisting of a hydroxyl group (OH) bearing a negative charge. It is the conjugate base of water and a key participant in acid–base chemistry, especially in aqueous solutions and industrial processes.

Structure and properties: The hydroxide ion has a bent geometry around the oxygen atom, with the negative charge localized primarily on oxygen. In water, it is highly solvated by hydrogen bonding, which stabilizes the ion and affects its reactivity. It behaves as a strong base in aqueous environments and readily participates in proton transfer and precipitation reactions.

Chemistry: As a Brønsted–Lowry base, OH− accepts a proton to form water: OH− + H+ → H2O. In Arrhenius terms, it is produced by the dissociation of bases in water, such as NaOH → Na+ + OH−. It can act as a nucleophile in organic reactions and forms metal hydroxide precipitates with many metal cations: M2+ + 2 OH− → M(OH)2(s). Hydroxide ions are also involved in the autoionization of water: 2 H2O ⇌ H3O+ + OH−, which establishes the pH balance of aqueous solutions.

Occurrence and production: Hydroxide occurs in minerals such as brucite Mg(OH)2 and portlandite Ca(OH)2. Industrially, it is produced by neutralization of acids or by electrolysis in the chlor-alkali process to yield sodium hydroxide, a major industrial base.

Applications and safety: OH− is central to chemical manufacturing, water treatment, and pH control. It is highly caustic and corrosive, capable of causing chemical burns upon contact and requiring appropriate handling and PPE.