a radioactive transuranic element of atomic number 96, having an atomic weight of 247 for its most stable isotope (half-life 1.6 x 107
years). The chemical symbol is Cm
"It was first prepared in 1944 by helium-ion bombardment of plutonium in a cyclotron by Glenn Seaborg and colleagues in California. It has never been detected in nature, though minute quantities may exist in uranium deposits as a consequence of the neutron flux there."