Promethium is a chemical element with the symbol Pm and atomic number 61. All of its isotopes are radioactive; it is one of only two such elements that are followed in the periodic table by elements with stable forms, a distinction shared with technetium. There are two possible sources for natural Pm, rare decays of natural europium-151, and various isotopes.
Practical applications exist only for chemical compounds of Pm-147, which are used in luminous paint, atomic batteries, and thickness-measurement devices, even though promethium-145 is the most stable Pm isotope. Because natural promethium is exceedingly scarce, it is typically synthesized by bombarding uranium-235 with thermal neutrons to produce promethium-147 as a fission product.
Uses of Promethium
- It is used only for research purposes, except for Pm-147, which can be found outside laboratories. This isotope does not emit gamma rays, and its radiation has a relatively small penetration depth into the matter and a relatively long half-life.
- Pm is used in pacemakers. Some signal lights use a luminous paint containing phosphor that absorbs the beta radiation emitted by promethium-147 and emits light.
Properties of Pm
- has 61 electrons, arranged in the configuration [Xe]4f56s2.
- Chemically, It is a lanthanide, which forms salts when combined with other elements. It shows only one stable oxidation state of +3.
- Since traces of the element in nature is exceedingly scarce, the element is typically synthesized by bombarding enriched uranium with thermal neutrons to produce promethium-147.
- Pm salts have a pink or red color that colors the surrounding air with a pale blue-green light.