|Hopkins and Harris of the University of Illinois-Urbana reported its discovery in 1926 which was made by fractionation of neodymium and samarium earths and X-ray analysis of the separated fractions. They suggested the name Illinium, (symbol Il) after the American state of Illinois. The discoverers noticed that the element #61 is radioactive and has a short half-life. In 1941 Quill, Law, Pool, and Kurbatov used the new Ohio State cyclotron to bombard Neodymium and Samarium with various projectiles. A number of radioactive isotopes were produced, presumably including one due to element #61 for which they proposed the name Cyclonium. In 1942 isotope of element #61 was conformed by Wu, Segre and Bethe during a bombardment of Neodymium and Praseodymium with neutrons. However chemical proof was lacking because of the difficulty in separating the rare earths from each other at that time.|
Isolation and identification of element #61 was finally made in 1945 (confirmed 1947) by A. Marinsky, Glendenin and Coryell. They worked for the Manhattan Project at Oak Ridge, Tennessee, where scientists had to create the fuel for an atomic bomb.
Coryell's spouse suggested the name "promethium" after Προμηθευς [Prometheus], who according to Greek mythology stole fire from Zeus and gave it to humans.
|Lanthanide promethium had been found in the Earth crust only after its discovery in artificial conditions. The natural promethium isotope is 147Pm, the product of 235U fission. 36 radioisotopes of promethium have been characterized, with the most stable being 145Pm with a half-life of 18 years.|