Question

What is meant by radioactive isotopes?

Answer 1

radioactive isotopes are isotope of radio active. elements
these are elements which have extra nucleus

Answer 2

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.