Promethium is a highly radioactive lanthanoid, a synthetic rare earth metal. In its pure state it is silver-gray and metallic, though it is almost always used as a compound. Its atomic number is 61; its atomic symbol is Pm. It has an atomic radius of 181 picometers, and a density of 7.26 grams per cubic centimetre. Isotopes of Promethium range in atomic mass from 134 to 155; its longest-lived isotope, Promethium 145, has a radioactive half life of 17.7 years, while its most common isotope, Prometheum 147, decays in only 2.6 years. Due to its very short half life, there is no known naturally occurring Prometheum on the Earth; it has, however, been detected in the electron spectra of distant stars in the Andromeda galaxy.
Prometheum is a normal byproduct of the nuclear fissioning of Uranium 238 and the radioactive decay of Europium 151. It can also be synthesized by bombarding the more common lanthanoid metal Neodymium with neutron radiation, or by ion-exchange technology. Promethium emits intense beta radiation and x-rays; care must be taken when handling it to avoid radiation exposure and radioactive contamination, as Promethium can be absorbed by the bones. Bohuslav Brauner, a German chemist, first predicted the existence of an element ‘between Neodymium and Samarium’ in 1902. Over the years Promethium is believed to have been produced in the laboratory by a number of groups, but it was not chemically isolated until 1945; the first confirmed sample of pure metallic Promethium was created at Oak Ridge National Lab by Jacob Marinsky, Lawrence Glendinin, and Charles Coryell. The name of the element was suggested by Coryell’s wife Grace Mary Coryell, and refers to Prometheus, the Titan of Greek myth who stole the secret of fire from the Gods and gave it to humanity.
Over 30 different compounds involving Prometheum have been created, but it is not commonly used in industrial or consumer applications. Prometheum compounds are often luminescent, and Prometheum has been used as a radioactive paint (particularly in watch dials). It is also used to create long-lived nuclear batteries, in which glowing Prometheum compounds provide a steady source of light which is used by a photovoltaic cell to generate electricity. Prometheum is also used as a beta radioactive emitter in guages used for quality control in manufacturing. It has been proposed, among other things, as a portable X-ray source and as a source of heat and power in the radioisotope thermoelectric generators used by deep space probes. However, when you get down to it, we don’t know a lot about the properties of Prometheum; its intense radioactivity, and the difficulty of synthesizing even small samples, limits its usefulness for anything beyond scientific experimentation.
Sources:
Los Alamos National Laboratory
WebElements.com
Jefferson Lab
Wikipedia: Prometheum
