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For nuclear batteries.
|Atomic Number:||61||Atomic Symbol:||Pm|
|Atomic Weight:||145||Electron Configuration:||2-8-23-8-2|
|Melting Point:||oC||Boiling Point:||oC|
|Description:||Radioactive rare earth metal.|
History(Prometheus, who, according to mythology, stole fire from
- 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
OccurenceSearches for the element on earth have been fruitless, and it
now appears that promethium is completely missing from the earth's crust.
Promethium, however, has been identified in the spectrum of the star HR465 in
- 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
- 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
- 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.
- 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
- More than 30 promethium compounds have been prepared.
- Most are colored.
CostsPromethium-147 is available at a cost of about 50c/Ci