There are three types of radioactivity and they are:

• Alpha decay: An alpha particle is a helium nucleus $$He_{2}^{4}$$. When a nucleus undergoes alpha decay, it transforms into a different nucleus by emitting alpha particles.
• Beta decay: Beta decay is a spontaneous process in which the nucleus undergoes decay by emitting either electrons or positron. Beta decay can be either beta plus decay or beta minus decay.
• Gamma decay: The energy difference between the energy states in a nucleus is responsible for gamma decay.