Promethium (pronEng|prəˈmiːθiəm/, /proʊˈmiːθiəm) is a
chemical elementwith the symbol Pm and atomic number61. It is notable for being the only other exclusively radioactive element besides technetiumwhich is followed by chemical elements that have stable isotopes.
Promethium's longest lived isotope 145Pm is a soft beta emitter with a half-life of 17.7 years. It does not emit
gamma rays, but beta particles impinging on elements of high atomic numbers can generate X-rays, and a sample of 145Pm does produce some such soft X-ray radiation in addition to beta particles.
Pure promethium exists in two
allotropicforms, and its chemistry is similar to other lanthanides. Promethium salts luminesce in the dark with a pale blue or greenish glow, due to their high radioactivity. Promethium can be found in traces in some uraniumores, as a fission product. Newly made promethium is also seen in the spectra of some stars.
Uses for promethium include:
* As a beta radiation source for thickness gauges.
* As a light source for signals that require reliable, independent operation (using
phosphorto absorb the beta radiation and produce light).
* In a
nuclear batteryin which cells convert the beta emissions into electric current, yielding a useful life of about five years, using Pm-147.
Promethium(III) chloride(PmCl3) mixed with zinc sulfide(ZnS) was used for time as a major luminous paint for watches after radiumwas discontinued. This mixture is still occasionally used for some luminous paint applications (though most such uses with radioactive materials have switched to tritiumfor safety reasons).
* Promethium has possible future uses in portable X-ray sources, and as auxiliary heat or power sources for space probes and satellites (although the alpha emitter
plutonium-238has become standard for most space-exploration related uses – see Radioisotope thermoelectric generators).
The existence of promethium was first predicted by
Bohuslav Braunerin 1902; this prediction was supported by Henry Moseleyin 1914, who found a gap for a missing element which would have atomic number 61, but was unknown (however, Moseley of course had no sample of the element to verify this). Several groups claimed to have produced the element, but they could not confirm their discoveries because of the difficulty of separating promethium from other elements. Promethium was first produced and proved to exist at Oak Ridge National Laboratory(ORNL) in 1945 by Jacob A. Marinsky, Lawrence E. Glendeninand Charles D. Coryellby separation and analysis of the fission products of uraniumfuel irradiated in the Graphite Reactor; however, being too busy with defense-related research during World War II, they did not announce their discovery until 1947. [cite journal | year = 2003 | title = Discovery of Promethium | journal = ORNL Review | volume = 36 | issue = 1 | url = http://www.ornl.gov/info/ornlreview/v36_1_03/article_02.shtml | accessdate = 2006-09-17 ] The name promethium is derived from Prometheus, the Titan, in Greek mythology, who stole the fire from Mount Olympus and brought it down to mankind. The name was suggested by Grace Mary Coryell, Charles Coryell's wife, who felt that they were stealing fire from the gods.
In 1963, ion-exchange methods were used at ORNL to prepare about 10 grams of promethium from nuclear reactor fuel processing wastes.
Today, promethium is still recovered from the byproducts of uranium fission; it can also be produced by bombarding 146Nd with
neutrons, turning it into 147Nd which decays into 147Pm through beta decay with a half-life of 11 days.
Promethium can be formed in nature as a product of
spontaneous fissionof uranium-238and alpha decayof europium-151. Only trace amounts can be found in naturally occurring ores: a sample of pitchblendehas been found to contain promethium at a concentration of four parts per quintillion (1018) by mass. [cite journal | last = Attrep | first = Moses, Jr. | coauthors = and P. K. Kuroda | year = 1968 | month = May | title = Promethium in pitchblende | journal = Journal of Inorganic and Nuclear Chemistry | volume = 30 | issue = 3 | pages = 699–703 | doi = 10.1016/0022-1902(68)80427-0 ] It was calculated that the equilibrium mass of promethium in the earth crustis about 560 g due to uranium fission and about 12 g due to the recently observed alpha decay of europium-151 [cite journal | author = P. Belli, R. Bernabei, F. Cappella, R. Cerulli, C.J. Dai, F.A. Danevich, A. d’Angelo, A. Incicchitti, V.V. Kobychev, S.S. Nagorny, S. Nisi, F. Nozzoli, D. Prosperi, V.I. Tretyak, S.S. Yurchenko | year = 2007 | month = | title = Search for α decay of natural Europium | journal = Nuclear Physics A | volume = 789 | issue = | pages = 15–29 | doi = 10.1016/j.nuclphysa.2007.03.001 ]
Promethium has also been identified in the spectrum of the star
HR 465in Andromeda, and possibly HD 101065 ( Przybylski's star) and HD 965. [cite journal | author = C. R. Cowley, W. P. Bidelman, S. Hubrig, G. Mathys, and D. J. Bord | year = 2004 | title = On the possible presence of promethium in the spectra of HD 101065 (Przybylski's star) and HD 965 | journal = Astronomy & Astrophysics | volume = 419 | pages = 1087–1093 | doi = 10.1051/0004-6361:20035726 ]
Promethium compounds include:
radioisotopes of promethium have been characterized, with the most stable being 145Pm with a half-lifeof 17.7 years, 146Pm with a half-life of 5.53 years, and 147Pm with a half-life of 2.6234 years. All of the remaining radioactiveisotopes have half-lives that are less than 364 days, and the majority of these have half lives that are less than 27 seconds. This element also has 11 meta states with the most stable being 148Pm"m" (T½ 41.29 days), 152Pm"m"2 (T½ 13.8 minutes) and 152Pm"m" (T½ 7.52 minutes).
The isotopes of promethium range in
atomic weightfrom 127.9482600 u (128Pm) to 162.9535200 u (163Pm). The primary decay modebefore the longest-lived isotope, 145Pm, is electron capture, and the primary mode after is beta minus decay. The primary decay products before 145Pm are neodymium(Nd) isotopes and the primary products after are samarium(Sm) isotopes.
tability of promethium isotopes
technetium, promethium is one of the two elements with atomic number less than 83 that have only unstable isotopes, which is a rarely occurring effect of the liquid drop modeland stabilities of neighbor element isotopes.
Promethium must be handled with great care because of its high radioactivity. In particular, promethium can emit
X-rays during its beta decay. Its half-life is less than that of plutonium-239 by a factor of about 1350, and its biological toxicity is correspondingly higher. Promethium has no biological role.
* [http://periodic.lanl.gov/elements/61.html Los Alamos National Laboratory – Promethium]
* [http://www.webelements.com/webelements/elements/text/Pm/index.html WebElements.com – Promethium]
* [http://education.jlab.org/itselemental/ele061.html It's Elemental – Promethium]
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Promethium — Prométhium Pour les articles homonymes, voir Pm. Prométhéum … Wikipédia en Français
prométhium — [ prɔmetjɔm ] n. m. • promethium 1953; de Prométhée ♦ Chim. Élément atomique (Pm; no at. 61; m. at. [isotope de plus longue période] 145) du groupe des lanthanides. Tous les isotopes connus du prométhium sont radioactifs. prométhium n. m. CHIM… … Encyclopédie Universelle
promethium — Symbol: Pm Atomic number: 61 Atomic weight: (147) Soft silvery metallic element, belongs to the lanthanoids. Pm 147, the only natural isotope, is radioactive and has a half life of 252 years. Eighteen radioisotopes have been produced, but all… … Elements of periodic system
promethium — radioactive element, long one of the missing elements, 1948, so called by discoverers Jacob Marinsky and Lawrence Glendenin, who detected it in 1945 in the fusion products of uranium while working on the Manhattan Project. From PROMETHEUS (Cf.… … Etymology dictionary
promethium — ☆ promethium [prō mē′thē əm ] n. [ModL: so named (1949) for earlier prometheum, name proposed by G. M. Coryell for element isolated (1948) by J. A. Marinsky & L. E. Glendenin, U.S. physicists < Gr Promētheus (see PROMETHEUS) in reference to… … English World dictionary
Promethium — Eigenschaften … Deutsch Wikipedia
Prométhium — Pour les articles homonymes, voir Pm. Prométhium Néodyme ← Prométhium → … Wikipédia en Français
promethium — /preuh mee thee euhm/, n. Chem. a rare earth, metallic, trivalent element. Symbol: Pm; at. no.: 61. [1945 50; < NL; see PROMETHEUS, IUM] * * * ▪ chemical element (Pm), chemical element, only rare earth metal of transition Group IIIb of the… … Universalium
Promethium — Pro|me|thi|um 〈n.; s; unz.; chem. 〉 zu den Metallen der Seltenen Erden gehörendes chem. Element, Ordnungszahl 61 [nach dem grch. Titanen Prometheus] * * * Pro|me|thi|um [nach der griech. Sagengestalt Prometheus; ↑ ium], das; s; Symbol: Pm;… … Universal-Lexikon
Promethium — prometis statusas T sritis fizika atitikmenys: angl. cyclonium; illinium; promethium vok. Promethium, n rus. прометий, m pranc. prométheum, m; prométhium, m … Fizikos terminų žodynas