Transcript: The three basic types of radioactive decay are called alpha, beta, and gamma decay. In the alpha process an atom spontaneously emits a helium nucleus. Helium nucleus contains two protons and two neutrons so alpha decay reduces the atomic number by two. In beta decay a neutron decays into a proton, an electron, and a neutrino. A neutron is only stable when bound in an atomic nucleus. Free neutrons will decay radioactively. The final type of emission is called gamma radiation. Gamma rays are high energy photons released spontaneously by radioactive atoms.