nonreactive

Nonreactive describes substances that do not readily undergo chemical reactions with other substances under specified conditions. In common usage it is synonymous with inert, especially in reference to chemistry and materials science.

Reactivity depends on conditions such as temperature, pressure, solvent, and the presence of catalysts. Many substances appear nonreactive because they have full valence electron shells or because reactions are kinetically hindered by high activation energies. Passivation can also render a surface nonreactive by forming a protective layer, as with many metals that develop oxide films.

Examples include the noble gases, which are highly nonreactive at room temperature due to having complete electron configurations. Some materials, like gold or silicon dioxide, show low reactivity with many reagents and are used in containers, sensors, and laboratory equipment. In biology or environmental contexts, nonreactive surfaces reduce adsorption and fouling.

Important caveats: nonreactive does not imply absolute immutability. Under extreme conditions—high temperature, strong oxidizers, or strong reducing agents—substances previously considered nonreactive can participate in reactions. In practical terms, chemists specify the conditions under which a substance is nonreactive.

Applications include creating inert atmospheres for chemical reactions, corrosion-resistant materials, packaging for sensitive compounds, and electronic or optical components where chemical stability is essential.

See also: inert, reactivity, passivation, inert atmosphere, corrosion resistance.