A radioactive isotopes are called radionuclides. Every element has radioactive isotopes. Each of them corresponds to different processes happening in atomic nuclei. These processes result in disintegration of a nucleus, and the overall process is called radioactive decay. As the result of these processes, nucleus of one element is transformed to nucleus of another element, a process called transmutation .
Beta radiation consists of a stream of electrons.
Electrons are generated within nucleus and ejected out of the atom. Gamma radiation consists of a stream of photons of very high energy. It usually accompanies the other types of radiation. Penetrating ability of different types of irradiation tells us which one is the most dangerous. In addition to breaking nuclei into parts one can combine them as well.