Question

What is a radioactive isotope?

Answer 1

Isotopes are atoms of the same element, with the same proton number but have different numbers of neutrons hence having different nucleon numbers.

Explanation:

Radioactive isotopes have unstable nuclei so they emit radiations in the form of beta, gamma and alpha rays. ( The radiations are the way in which the nuclei "surrender" excess energy)
https://www.britannica.com/science/radioactive-isotope