After enough energy is released, the atom returns to a stable state and is no longer radioactive. All radioactive materials eventually decay, just not at the same rate. Alpha, Beta, & Gamma Rays. The extra energy, or radiation, emitted by radioactive elements comes in three different types: alpha, beta, and gamma. Alpha radiation is a stream of alpha particles, which are positively charged. They're fairly large, which means they have a difficult time getting through materials like clothes and paper.