The name given to an isotope whose nucleus is unstable is radioisotope (also called a radionuclide).

Quick Scoop

  • An isotope with an unstable nucleus tends to decay over time, emitting radiation in order to become more stable.
  • Because it emits radiation, such an isotope is called a radioisotope or radionuclide in nuclear chemistry and physics.
  • Many elements have both stable isotopes (do not decay) and unstable, radioactive isotopes (radioisotopes) that are used in medicine, power generation, and research.

So if you see a question asking “what is the name given to an isotope if its nucleus is unstable?”, the one-word answer to enter is: radioisotope.

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