What is radio isotopes?

Radioactive isotope, also called radioisotope, radionuclide, or radioactive nuclide, any of several species of the same chemical element with different masses whose nuclei are unstable and dissipate excess energy by spontaneously emitting radiation in the form of alpha, beta, and gamma rays.

Any of the same chemical element with different masses whose nuclei are unstable and gets energy by emitting radiation in the form of alpha, beta, and gamma rays.