Radioisotopes

thumb|Chart of known nuclides . The vast majority are radionuclides.

thumb|right|γ-ray spectrum of cobalt-60

Iodine-131 (131I, I-131) is a radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. It has a radioactive decay half-life of about eight days. It is associated with nuclear energy, medical diagnostic and treatment procedures, and natural gas production. It also plays a major role as a radioactive isotope present in nuclear fission products, and was a significant contributor to the health hazards from open-air atomic bomb testing in the 1950s, and from the Chernobyl disaster, as well as being a large fraction of the contamination

Xenon-135 (135Xe) is an unstable isotope of xenon with a half-life of 9.14 hours, decaying to long-lived caesium-135.