- One of two or more nuclides that are chemically identical, having the same number of protons, yet differ in mass number, since their nuclei contain different numbers of neutrons; individual isotopes are named with the inclusion of their mass number in the superior position (12C) and the atomic number (nuclear protons) in the inferior position (6C). In former usage, the mass numbers follow the chemical symbol (C-12). [iso- + G. topos, part, place]- daughter i. an element produced by radioactive decay of another. See radionuclide generator, cow.- radioactive i. an i. with an unstable nuclear composition; such nuclei decompose spontaneously by emission of a nuclear electron (β particle) or helium nucleus (α particle) and radiation (γ rays), thus achieving a stable nuclear composition; used as tracers and as radiation and energy sources. See half-life.- stable i. a nonradioactive nuclide; an i. that shows no tendency to undergo radioactive decomposition.
* * *iso·tope 'ī-sə-.tōp n1) any of two or more species of atoms of a chemical element with the same atomic number and position in the periodic table and nearly identical chemical behavior but with differing atomic mass or mass number and different physical properties2) NUCLIDEiso·to·pic .ī-sə-'täp-ik, -'tō-pik adjiso·to·pi·cal·ly -'täp-i-k(ə-)lē, -'tō-pi- adv
* * *n.any one of the different forms of an element, possessing the same number of protons (positively charged particles) in the nucleus, and thus the same atomic number, but different numbers of neutrons. Isotopes therefore have different atomic weights. Radioactive isotopes decay into other isotopes or elements, emitting alpha, beta, or gamma radiation. Some radioactive isotopes may be produced artificially by bombarding elements with neutrons. These are known as nuclides and are used extensively in radiotherapy for the treatment of cancer.
* * *iso·tope (iґso-tōp″) [iso- + -tope] a chemical element having the same atomic number as another (i.e., the same number of nuclear protons) but possessing a different atomic mass (i.e., a different number of nuclear neutrons).
Medical dictionary. 2011.