Radiation and Radiological Disasters. (1) An atom or molecule that has too many or too few electrons, causing it to have an electrical charge, and therefore, be chemically active (2) An electron that is not associated (in orbit) with a nucleus
U.S. Environmental Protection Agency, Radiation Glossary, Office of Radiation and Indoor Air Radiation Protection Division, Washington, DC, USA 2013. http://www.epa.gov/radiation/glossary/index.html#a , (Dzstr/ Rad Emr - Amer) {823}