Hierarchy classification:

1. top of the aat hierarchies
2. Materials Facet
3. Materials (hierarchy name)
4. materials (substances)
5. [materials by form]
6. [materials by chemical form]
7. isotopes

Anotations

Scope note:

All chemical elements possess one or more types of unstable as well as stable isotopes. The former are known as radioisotopes or radioactive isotopes. Their nuclei dissipate excess energy as alpha, beta, and gamma rays. This radioactive decay forms the basis for the measuring processes of radioactive dating.