Zn2aq

Zn2aq is the notation used in chemistry to denote zinc(II) ions in aqueous solution, typically represented as Zn2+(aq). In dilute aqueous solutions, zinc exists predominantly as the hexaaqua complex [Zn(H2O)6]2+. This octahedral complex is colorless and diamagnetic due to its d10 configuration; zinc(II) is a hard Lewis acid that preferentially binds oxygen donors.

At low to moderate pH, the aquated zinc remains as [Zn(H2O)6]2+. As pH increases, hydrolysis occurs: [Zn(H2O)5(OH)]+ forms first, and at higher pH, Zn(OH)2(s) can precipitate, typically around pH 9–10. The aquated Zn2+ can also form various hydroxy- and aquo- complexes with ligands, depending on solution composition.

Zn2+(aq) forms a wide range of complexes with ligands such as inorganic anions (carbonate, sulfate, phosphate) and organic ligands (glycine, citrate, EDTA) in aqueous solution; stability constants vary widely. In biology, Zn2+ is an essential micronutrient that acts as a catalytic and structural cofactor in many enzymes and proteins. In cells, free Zn2+ is tightly buffered, and transient Zn2+ fluxes can participate in signaling in some organisms.

In environmental and analytical contexts, Zn2+(aq) is measured by atomic spectroscopy or chromatography, and its mobility is influenced by complexation and pH. Industrially, zinc salts are dissolved in water to form Zn2+ solutions for plating, battery chemistry, and catalysis.