hydroxido

Hydroxido is the term used in several Romance-language contexts to denote the chemical species known in English as hydroxide. In chemistry, the most common reference is to the hydroxide ion, OH−, a negatively charged polyatomic anion consisting of one oxygen atom bonded to one hydrogen atom. The overall negative charge is localized largely on the oxygen, and the ion is typically described as having a single O–H bond with two lone pairs on oxygen.

Hydroxide ions are central to acid–base chemistry. In aqueous solution they act as bases, accepting protons to form water and increasing the solution’s pH. They are produced when soluble bases dissociate in water (for example, NaOH → Na+ + OH−) and are consumed when bases are neutralized by acids. The hydroxide ion also participates in a wide range of nucleophilic reactions, especially in organic and inorganic synthesis.

Occurrence and sources include dissolution of alkali and alkaline earth metal hydroxides in water, salts containing the OH− anion, and minerals such as brucite (Mg(OH)2) and goethite (FeO(OH)). In biology and environmental chemistry, hydroxide concentration is a key component of pH regulation and ecological processes.

It is important to distinguish hydroxide from related but different species: the hydroxyl group (−OH) found in many organic compounds, which is neutral, and the hydroxyl radical (OH•), a highly reactive neutral species. Both the hydroxide ion and these related forms play distinct roles in chemistry, biology, and environmental science.