The main properties of each type of radiation are briefly discussed below. Alpha particles consist of two protons and two neutrons and carry a positive charge. They are emitted with high energy from the nucleus of heavy elements during radioactive decay, but lose energy rapidly in passing through material. A couple sheets of paper are sufficient to stop most alpha particles. Since they cannot penetrate even the outer dead layer of our skin, they are not an external hazard.
Beta particles are electrons emitted from nucleus of atoms at nearly the speed of light.
They have a very small mass compared to protons or neutrons and carry a negative charge. Very energetic beta particles can penetrate inch of wood. Gamma rays are electromagnetic energy waves emitted from the nucleus of atoms and have no charge. X-rays are the same as gamma rays, except they originate outside the nucleus from processes involving electrons. These differ from X-rays and gamma rays only in wave frequency and energy.