NO3ion

NO3ion is a term that is commonly used to refer to the nitrate ion, NO3−, a polyatomic anion central to inorganic chemistry and environmental science. The ion features one central nitrogen atom bonded to three oxygen atoms in a trigonal planar arrangement. Through resonance, the three N–O bonds are equivalent, and the formal oxidation state of nitrogen is +5. In aqueous solutions and in most solid nitrates, NO3− carries a −1 charge and behaves as a very weak base since it is the conjugate base of the strong acid nitric acid.

NO3− occurs widely in nature and industry. It is formed in soils and waters through natural processes such as nitrification and microbial cycling, and can be released by volcanic activity or the decomposition of organic matter. Industrially, nitrates are prepared by neutralizing nitric acid with bases to form salts such as sodium nitrate (NaNO3), potassium nitrate (KNO3), and calcium nitrate (Ca(NO3)2). These salts are highly soluble in water and are used in diverse applications.

In chemistry, nitrate acts primarily as an oxidizing agent. It can be reduced under appropriate conditions to nitrite (NO2−) or to molecular nitrogen in denitrification processes. Nitrate salts are important as fertilizers, contributing essential nitrogen to agriculture, and as components in explosives and propellants. Environmental concerns include nitrate contamination of drinking water and eutrophication from agricultural runoff, which can impact aquatic ecosystems.

See also: nitrate, nitrite, nitrogen cycle, fertilizers, denitrification.