Promethium

Promethium was the last of the rare earth lanthanide elements to be discovered. In 1926, American chemist B. Smith Hopkins at the University of Illinois, claimed that the element had been found in rare-earth residues of monazite and he named it illinium, after his college and state. Hopkins thought that the element was radioactive with a short half-life.

However, Hopkins was not the only one to put in claims on the element: Italian chemist Luigi Rolla at the Royal University in Florence also claimed to have found the element in 1924. However, the right went to the holder of evidence that the element had, in fact, been produced- Jacob A. Marinsky.

The element was named after the Greek god Prometheus, who is famous in mythology for stealing fire from Mount Olympus to give to people.

 It was later found out that Hopkins was indeed correct- promethium is radioactive and should be handled VERY carefully. It was also discovered that it is the ONLY rare earth radioactive metal. Because out the radioactivity, its salts glow pale blue or green in the dark. The only current known way to produce promethium is through uranium fission.