Promethium

Atomic Number:	61	Atomic Symbol:	Pm
Atomic Weight:	145	Electron Configuration:	2-8-23-8-2
Shells:	2,8,18,23,8,2	Filling Orbital:	4f5
Melting Point:	oC	Boiling Point:	oC
Description:	Radioactive rare earth metal.
Uses:

Group	Period	Index

History

• In 1902 Branner predicted the existence of an element between neodymium and samarium, and this was confirmed by Moseley in 1914.
• In 1941, workers at Ohio State University irradiated neodymium and praseodymium with neutrons, deuterons, and alpha particles, and produced several new radioactivities, which most likely were those of element 61.
• Wu and Segre, and Bethe, in 1942, confirmed the formation; however, chemical proof of the production of element 61 was lacking because of the difficulty in separating the rare earths from each other at that time.
• In 1945, Marinsky, Glendenin, and Coryell made the first chemical identification by use of ion-exchange chromatography.
• Their work was done by fission of uranium and by neutron bombardment of neodymium.

Occurence

Isotopes

• This element is being formed recently near the star's surface, for no known isotope of promethium has a half-life longer than 17.7 years.
• Seventeen isotopes of promethium, with atomic masses from 134 to 155 are now known.
• Promethium-147, with a half-life of 2.6 years, is the most generally useful.
• Promethium-145 is the longest lived, and has a specific activity of 940 Ci/g.

Properties

• It is a soft beta emitter; although no gamma rays are emitted, X-radiation can be generated when beta particles impinge on elements of a high atomic number, and great care must be taken in handling it.
• Promethium salts luminesce in the dark with a pale blue or greenish glow, due to their high radioactivity.
• Ion-exchange methods led to the preparation of about 10 g of premethium from atomic reactor fuel processing wastes in early 1963.
• Little is yet generally known about the properties of metallic promethium.
• Two allotropic modifications exist.

Uses

• The element has applications as a beta source for thickness gages, and it can be absorbed by a phosphor to produce light.
• Light produced in this manner can be used for signs or signals that require dependable operation; it can be used as a nuclear-powered battery by capturing light in photocells which convert it into electric current.
• Such a battery, using 147Pm, would have a useful life of about 5 years.
• Promethium shows promise as a portable X-ray source, and it may become useful as a heat source to provide auxiliary power for space probes and satellites.
• More than 30 promethium compounds have been prepared.
• Most are colored.

Costs