Promethium: Difference between revisions
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'''Promethium''' ({{pronEng|prəˈmiːθiəm/, /proʊˈmiːθiəm}}) is a [[chemical element]] with the symbol '''Pm''' and [[atomic number]] 61. It is notable for being the only other exclusively radioactive element besides [[technetium]] which is followed by chemical elements that have stable [[isotopes]]. |
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== Characteristics == |
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Promethium's longest lived isotope <sup>145</sup>Pm is a soft [[beta particle|beta]] emitter with a half-life of 17.7 years. It does not emit [[gamma ray]]s, but beta particles impinging on elements of high atomic numbers can generate [[X-ray]]s, and a sample of <sup>145</sup>Pm does produce some such soft X-ray radiation in addition to beta particles. |
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Pure promethium exists in two [[allotropic]] forms, and its chemistry is similar to other [[lanthanide]]s. 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 [[uranium]] ores, as a fission product. Newly made promethium is also seen in the spectra of some stars. |
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== Applications == |
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Uses for promethium include: |
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* As a beta radiation source for thickness gauges. |
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* As a light source for signals that require reliable, independent operation (using [[phosphor]] to absorb the beta radiation and produce light). |
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* In a [[nuclear battery]] in which cells convert the beta emissions into electric current, yielding a useful life of about five years, using [[Pm-147]]. |
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* [[Promethium(III) chloride]] (PmCl<sub>3</sub>) mixed with [[zinc sulfide]] ([[Zinc|Zn]][[Sulfur|S]]) was used for a time as a major luminous paint for watches after [[radium]] was discontinued. This mixture is still occasionally used for some luminous paint applications (though most such uses with radioactive materials have switched to [[tritium]] for safety reasons). |
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* 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-238]] has become standard for most space-exploration related uses – see [[Radioisotope thermoelectric generators]]). |
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== History == |
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The existence of promethium was first predicted by [[Bohuslav Brauner]] in 1902; this prediction was supported in 1914 by [[Henry Moseley]] who, having discovered that [[atomic number]] was an experimentally measurable property of elements, found that no known element had atomic number 61. 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. Glendenin]] and [[Charles D. Coryell]] by separation and analysis of the fission products of [[uranium]] fuel irradiated in the [[X-10 Graphite Reactor|Graphite Reactor]]; however, being too busy with defense-related research during [[World War II]], they did not announce their discovery until 1947.<ref>{{cite journal | year = 2003 | title = Discovery of Promethium | journal = [[Oak Ridge National Laboratory|ORNL]] Review | volume = 36 | issue = 1 | url = http://www.ornl.gov/info/ornlreview/v36_1_03/article_02.shtml | accessdate = 2006-09-17 }}</ref> 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. |
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In 1963, ion-exchange methods were used at ORNL to prepare about ten grams of promethium from nuclear reactor fuel processing wastes. |
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Today, promethium is still recovered from the byproducts of uranium fission; it can also be produced by bombarding <sup>146</sup>Nd with [[neutron]]s, turning it into <sup>147</sup>Nd which decays into [[promethium-147|<sup>147</sup>Pm]] through beta decay with a half-life of 11 days. |
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== Occurrence == |
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Promethium can be formed in nature as a product of [[spontaneous fission]] of [[uranium-238]] and [[alpha decay]] of [[europium]]-151. Only trace amounts can be found in naturally occurring ores: a sample of [[pitchblende]] has been found to contain promethium at a concentration of four parts per quintillion (10<sup>18</sup>) by mass.<ref>{{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 }}</ref> It was calculated that the equilibrium mass of promethium in the [[earth's crust]] is about 560 g due to uranium fission and about 12 g due to the recently observed alpha decay of europium-151 <ref>{{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 }}</ref> |
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Promethium has also been identified in the spectrum of the star [[HR 465]] in [[Andromeda (constellation)|Andromeda]], and possibly HD 101065 ([[Przybylski's star]]) and HD 965.<ref>{{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 }}</ref> |
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== Compounds == |
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Promethium compounds include: |
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* Chlorides |
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** [[promethium(III) chloride|PmCl<sub>3</sub>]] |
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* Bromides |
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** [[Promethium(III) bromide|PmBr<sub>3</sub>]] |
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* Oxides |
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** [[promethium(III) oxide|Pm<sub>2</sub>O<sub>3</sub>]] |
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== Isotopes == |
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{{main|isotopes of promethium}} |
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Thirty-six [[radioisotope]]s of promethium have been characterized, with the most stable being <sup>145</sup>Pm with a [[half-life]] of 17.7 years, <sup>146</sup>Pm with a half-life of 5.53 years, and [[promethium-147|<sup>147</sup>Pm]] with a half-life of 2.6234 years. All of the remaining [[radioactive]] isotopes 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 state]]s with the most stable being <sup>148</sup>Pm<sup>''m''</sup> (T<sub>½</sub> 41.29 days), <sup>152</sup>Pm<sup>''m''2</sup> (T<sub>½</sub> 13.8 minutes) and <sup>152</sup>Pm<sup>''m''</sup> (T<sub>½</sub> 7.52 minutes). |
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The isotopes of promethium range in [[atomic weight]] from 127.9482600 [[atomic mass unit|u]] (<sup>128</sup>Pm) to 162.9535200 u (<sup>163</sup>Pm). The primary [[decay mode]] before the longest-lived isotope, <sup>145</sup>Pm, is [[electron capture]], and the primary mode after is [[beta minus decay]]. The primary [[decay product]]s before <sup>145</sup>Pm are [[neodymium]] (Nd) isotopes and the primary products after are [[samarium]] (Sm) isotopes. |
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===Stability of promethium isotopes=== |
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Along with [[technetium]], promethium is one of only two elements with atomic number less than 83 that have only unstable isotopes, which is a [[Technetium#Stability of technetium isotopes|rarely occurring effect]] of the [[liquid drop model]] and stabilities of neighbor element isotopes. |
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== Precautions == |
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Promethium must be handled with great care because of its '''high radioactivity'''. In particular, promethium can emit [[X-ray]]s 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. |
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== References == |
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<!-- See [[Wikipedia:Footnotes]] for instructions. --> |
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<references /> |
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*[http://periodic.lanl.gov/elements/61.html Los Alamos National Laboratory – Promethium] |
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== External links == |
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{{Commons|Promethium}} |
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{{wiktionary|promethium}} |
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* [http://www.webelements.com/webelements/elements/text/Pm/index.html WebElements.com – Promethium] |
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* [http://education.jlab.org/itselemental/ele061.html It's Elemental – Promethium] |
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{{clear}} |
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{{Compact periodic table}} |
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[[Category:Chemical elements]] |
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[[Category:Lanthanides]] |
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[[Category:Synthetic elements]] |
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[[ar:بروميثيوم]] |
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[[bn:প্রমিথিয়াম]] |
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[[he:פרומטיום]] |
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[[kn:ಪ್ರೊಮೆಥಿಯಮ್]] |
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[[mr:प्रोमेथियम]] |
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[[ja:プロメチウム]] |
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[[pl:Promet]] |
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[[ru:Прометий]] |
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[[scn:Promezziu]] |
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[[simple:Promethium]] |
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[[th:โพรมีเทียม]] |
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[[vi:Promethi]] |
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[[tr:Prometyum]] |
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[[uk:Прометій]] |
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Revision as of 20:54, 20 February 2009
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