Discovered : by J.A. Marinsky and co-workers in 1945 Isolated in Oak Ridge, Tennessee, USA Origin : The element is named after Prometheus, who in Greek mythology stole fire from the gods. Description : A radioactive element whose longest lived isotope, promethium-145, has a half-life of only 18 years. It is obtained in milligramme amounts from nuclear reactors, and a little is used in specialised miniature batteries. Image : Atlas witnesses Zeus' punishment of Prometheus.