- a radioactive element not found in nature but discovered in 1944 among the products of plutonium after bombardment by high-energy helium ions. Symbol: Cm; atomic number: 96.
- a silvery-white metallic transuranic element artificially produced from plutonium. Symbol: Cm; atomic no: 96; half-life of most stable isotope, 247 Cm: 1.6 x 10 7 years; valency: 3 and 4; relative density: 13.51 (calculated); melting pt: 1345±400°C
