scission

Scission is the act of cutting, splitting, or cleaving one object into two or more parts. In science, it describes the breakage of chemical bonds, the fragmentation of polymers, or the division of nuclei during fission. The term derives from Latin scindere, to cut apart.

In chemistry, bond scission refers to the cleavage of covalent bonds to form smaller fragments. Cleavage can be homolytic, with one electron going to each fragment to form radicals, or heterolytic, with both electrons moving to one fragment to produce ions. Rates depend on bond strength, environment, and catalysts or radicals.

In polymer science, chain scission denotes the breaking of the main chain within a polymer. It lowers molecular weight and viscosity and can weaken mechanical properties. Scission occurs under heat, chemical attack, radiation, or mechanical stress, and is a major factor in aging and processing.

In nuclear physics, scission refers to the splitting of a heavy nucleus into lighter nuclei, known as fission. The event releases energy and neutrons and can occur spontaneously or be induced by particles. The products depend on the material and reaction conditions.

In biology and biochemistry, scission is used to describe cleavage or fragmentation of biomolecules or cells, such as DNA strand scission or polysaccharide cleavage. More specific terms—cleavage, hydrolysis, or proteolysis—are often used to indicate the particular bond-breaking process.