Radiation

Sprays or streams of invisibly small particles are often referred to as particulate radiation because they carry energy along with them as they fly through space. They may be produced deliberately in machines such as particle accelerators, or they may be emitted spontaneously from radioactive materials. Alpha particles and beta particles are emitted by radioactive materials, while beams of electrons, protons, mesons, neutrons, ions, and even whole atoms and molecules can be produced in accelerators, nuclear reactors, and other kinds of laboratory apparatus.

The only particulate radiations that might be encountered outside of a laboratory are the alpha and beta particles that are emitted by radioactive materials. These are charged subatomic particles: the alpha particle has an electric charge of +2 and the beta particle has a charge of +1 or -1. Because of their electric charges, these particles attract or repel electrons in the atoms of any material through which they pass, thereby ionizing those atoms. If enough of these ionized atoms happen to be parts of essential molecules in a human body, the body's chemistry can be altered, with unhealthful consequences.