Many radioactive decays result in the formation of isotopes which are themselves radioactive and decay further.When a radioactive isotope decays its daughter nucleus may itself be unstable and decays into an α or β- or β+ emitter depending on where it is relative to the stability belt. The series of decays can be represented on a decay graph.In nature, the presence of radioactive isotopes is due to isotopes in the decay chains having long half-lives.