Why are isotopes radioactive and what factors contribute to their ability to emit radiation?

Isotopes are radioactive because they have an unstable nucleus, which means they have an imbalance of protons and neutrons. This imbalance causes the nucleus to emit radiation in the form of alpha particles, beta particles, or gamma rays. Factors that contribute to their ability to emit radiation include the number of protons and neutrons in the nucleus, as well as the energy levels of the particles within the nucleus.