(ī'sŏ-tōp‵ )

[iso- + Gr. topos, place (chemical isotopes occupy the same place on the periodic table)]

One of a series of chemical elements that have nearly identical chemical properties but different atomic weights and electric charges. Many isotopes are radioactive.

radioactive i.An isotope in which the nucleus is unstable and emits ionizing radiation such as gamma rays.

SEE: table - Radioactive Isotopes Having Important Long-Term Health Effects.

stable i.An isotope that does not undergo radioactive decay into another element.