Promethium is extremely rare, with only about 0.5 kg naturally occurring in Earth’s crust at any given time. Conceptual art shows the rare earth element promethium in a vial surrounded by an organic ligand. Image credit: Jacqueline DeMink / Thomas Dyke / ORNL. Discovered in 1945 at Clinton Laboratories, promethium is a lanthanide element with symbol Pm and atomic number 61. It is named after the mythological Titan who delivered fire to humans and...
