triatomic

Triatomic is a term used in chemistry to describe a species composed of three atoms. It applies to molecules made of three atoms, regardless of whether the atoms are identical or different, as well as to triatomic ions and radicals. Triatomic species are among the simplest multi-atom molecules and occur widely in inorganic, organic, and atmospheric chemistry.

Geometries of triatomic molecules vary. The arrangement is described by the VSEPR model and depends on the central atom and its valence electrons. Some triatomic molecules are linear, as in carbon dioxide (CO2). Others are bent or angular, as in water (H2O) and sulfur dioxide (SO2). Bond angles reflect these shapes, with CO2 near 180 degrees and H2O around 104.5 degrees; SO2 is typically about 119 degrees. Nitrogen dioxide (NO2) is another bent example. In molecules such as ozone (O3), resonance leads to delocalized bonding and a geometry that is not simply two single bonds.

Common examples of triatomic molecules include CO2, H2O, O3, NO2, and SO2. These species are important in multiple contexts: water is essential for life, ozone absorbs ultraviolet radiation, and carbon dioxide is a greenhouse gas. Triatomic molecules also appear in various chemical reactions, atmospheric processes, and biological systems, illustrating the wide relevance of three-atom species in science.

Triatomic species can be neutral molecules, ions, or radicals with unpaired electrons. Their study spans spectroscopy, reaction kinetics, and thermodynamics, contributing to areas from environmental science to materials chemistry.