Whilst a lot of lanthanides were discovered in the late 1800’s its was not until 1945 that Promethium was produced in the lab from the fission of uranium products. Promethium-147 was isolated by ion exchange chromatography. It was named after the Greek Titan Prometheus who in mythology stole fire from the gods of Mt Olympus. Promethium is the only rare earth metal that is radioactivity. In the dark it will produce a pale blue glow due to its radioactivity. Promethium has uses as a source of beta particles and is used in atomic batteries and missiles. It does not exist in nature and must be produced in the lab. Promethium was the last of the rare earth lanthanides to be discovered. It is a solid metal at room temperature with a melting point of 1042°c and a boiling point of 3000°c.
J.A. Marinsky, L.E. Glendenin, C.D. Coryell