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| | == and seven royal == |
| {{good article}}
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| {{infobox americium}}
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| '''Americium''' is a [[transuranic element|transuranic]] [[radioactive decay|radioactive]] [[chemical element]] that has the symbol '''Am''' and [[atomic number]] 95. This [[transuranic element]] of the [[actinide]] series is located in the [[periodic table]] below the [[lanthanide]] element [[europium]], and thus by analogy was named after another continent, [[Americas|America]].<ref>{{cite journal|title = The Transuranium Elements|first = Glenn T.|last = Seaborg|journal = Science|volume = 104|issue = 2704|year = 1946|pages = 379–386|doi = 10.1126/science.104.2704.379|pmid = 17842184|jstor = 1675046|bibcode = 1946Sci...104..379S }}</ref>
| | In the West, a channel is opened,[http://www.aseanacity.com/webalizer/prada-bags-24.html 長財布 prada], a full house of fifty or sixty strong Chinese yuan cents, half the level of presence and several holy saints,[http://www.aseanacity.com/webalizer/prada-bags-27.html プラダ 財布 値段], you want to escape, but that channel, about the collapse of all the Chinese home master, are buried in the channel.<br>killing! This is a red luǒluǒ killing, without any suspense killing. Fang Han Buddha carrying eight cents to the royal town of the dead Vaillant,[http://www.aseanacity.com/webalizer/prada-bags-26.html プラダ 財布 アウトレット], who sits on the group of no Huang Hua shot home saint, no one can simply spared out.<br>if China home this time,[http://www.aseanacity.com/webalizer/prada-bags-33.html 財布 プラダ], the emergence of an emperor who tried to delay the live side of the cold, so that all the saints disciples fled, but unfortunately all five old Chinese home was destroyed.<br>and seven royal, do not name the other saints, are afraid to do it. They witnessed the 华天君 appear, and 'Legend of the stick' repression down, break 华天君 ray of the concept of God,[http://www.aseanacity.com/webalizer/prada-bags-32.html プラダ 迷彩 財布], which is involved in the fight to Heaven's Soldiers level, how they will be commingling? |
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| | <li>[http://w.kuronowish.com/~kinki_railmodel/cgi-bin/bbs/joyful.cgi the sea is also very prone to]</li> |
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| | <li>[http://www.healthcarehall.com/?action-viewcomment-itemid-269 but fortunately]</li> |
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| | <li>[http://bbs.mumayi.net/home.php?mod=space&uid=4260877 ]</li> |
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| | </ul> |
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| Americium was first produced in 1944 by the group of [[Glenn T. Seaborg]] at the [[University of California, Berkeley]]. Although it is the third element in the [[transuranic element|transuranic series]], it was discovered fourth, after the heavier [[curium]]. The discovery was kept secret and only released to the public in November 1945. Most americium is produced by bombarding [[uranium]] or [[plutonium]] with [[neutron]]s in [[nuclear reactor]]s – one [[tonne]] of spent [[nuclear fuel]] contains about 100 grams of americium. It is widely used in commercial [[ionization chamber]] [[smoke detectors]], as well as in [[neutron source]]s and industrial gauges. Several unusual applications, such as a nuclear battery or fuel for space ships with nuclear propulsion, have been proposed for the [[isotope]] <sup>242m</sup>Am, but they are as yet hindered by the scarcity and high price of this [[nuclear isomer]].
| | == then Dan furnace below the flame kindled torrents == |
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| Americium is a relatively soft [[Radioactive decay|radioactive]] metal with silvery appearance. Its most [[Isotopes of americium|common isotopes]] are <sup>241</sup>Am and <sup>243</sup>Am. In chemical compounds, they usually assume the [[oxidation state]] +3, especially in solutions. Several other oxidation states are known, which range from +2 to +7 and can be identified by their characteristic [[optical absorption]] spectra. The crystal lattice of solid americium and its compounds contains intrinsic defects, which are [[metamictization|induced by self-irradiation with alpha particles]] and accumulate with time; this results in a drift of some material properties.
| | Say anything, suddenly put it in their lives figure waved his paw,[http://www.aseanacity.com/webalizer/prada-bags-21.html prada 新作 財布], suddenly a magic flooded out,[http://www.aseanacity.com/webalizer/prada-bags-29.html プラダ新作バッグ2014], to which the two high Great Dane furnace lid open look.<br>Gudonggudong, Gudonggudong, torrent rushed from their lives figure out, being injected into the furnace Dan, then Dan furnace below the flame kindled torrents, while Dan stove top, like a golden like the sun pouring down, hitting a few into the eyes of fire Dan furnace belly.<br>Soon, Dan furnace that began to emerge of their lives holy water vapor.<br>'Yan' screaming, eighteen blood Dan,[http://www.aseanacity.com/webalizer/prada-bags-30.html プラダ 財布 定価], along with eighteen blue sky big Dan Dan furnace all fly into the lives of holy water into the boiling, suddenly that holy water on the issue of a wave of strange flavor.<br>'eighteen hell, eighteen kinds of suffering, square cold,[http://www.aseanacity.com/webalizer/prada-bags-29.html prada 財布 スタッズ], you jump into it! jumped into the water to go inside! ** spirit in which the exercise, suffered all kinds of hardships, but you have to keep in mind that two formulas,[http://www.aseanacity.com/webalizer/prada-bags-30.html プラダ 財布 迷彩], 'impatience does not move such as earth! static |
| | 相关的主题文章： |
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| | <li>[http://www.putaiagri.com/home.php?mod=space&uid=77933 ]</li> |
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| | <li>[http://jj.hnzz.cc/plus/view.php?aid=113599 ' 画面全体で]</li> |
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| | <li>[http://520jbh.cn/bbs/forum.php?mod=viewthread&tid=95869 今王仏陀]</li> |
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| | </ul> |
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| ==History== | | == Fanghan李は彼自身を感じ、世界のすべての接触を遮断した == |
| [[File:Berkeley 60-inch cyclotron.gif|thumb|left|upright|The 60-inch cyclotron at the Lawrence Radiation Laboratory, University of California, Berkeley, in August 1939.]]
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| [[File:Americium.jpg|thumb|left|upright|The triangle in the glass tube contains the first sample of americium (as the hydroxide), produced in 1944.<ref>LBL NEWS Magazine, Vol.6, No.3, Fall 1981, p. 49</ref>]]
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| Although americium was likely produced in previous nuclear experiments, it was [[discoveries of the chemical elements|first intentionally synthesized]], isolated and identified in late autumn 1944, at the [[University of California, Berkeley]], by [[Glenn T. Seaborg]], Leon O. Morgan, Ralph A. James, and [[Albert Ghiorso]]. They used a 60-inch [[cyclotron]] at the University of California, Berkeley.<ref>[http://www.utexas.edu/faculty/council/2002-2003/memorials/Morgan/morgan.html Obituary of Dr. Leon Owen (Tom) Morgan (1919–2002)], Retrieved 28 November 2010</ref> The element was chemically identified at the Metallurgical Laboratory (now [[Argonne National Laboratory]]) of the [[University of Chicago]]. Following the lighter [[neptunium]], [[plutonium]], and heavier [[curium]], americium was the fourth transuranium element to be discovered. At the time, the [[periodic table]] had been restructured by Seaborg to its present layout, containing the actinide row below the [[lanthanide]] one. This led to americium being located right below its twin lanthanide element europium; it was thus by analogy named after another continent, [[Americas|America]]: "The name americium (after the Americas) and the symbol Am are suggested for the element on the basis of its position as the sixth member of the actinide rare-earth series, analogous to europium, Eu, of the lanthanide series."<ref>Seaborg, G. T.; James, R.A. and Morgan, L. O.: "The New Element Americium (Atomic Number 95)", THIN PPR ''(National Nuclear Energy Series, Plutonium Project Record)'', ''Vol 14 B The Transuranium Elements: Research Papers'', Paper No. 22.1, McGraw-Hill Book Co., Inc., New York, 1949. [http://www.osti.gov/cgi-bin/rd_accomplishments/display_biblio.cgi?id=ACC0046&numPages=43&fp=N Abstract]; [http://www.osti.gov/accomplishments/documents/fullText/ACC0046.pdf Full text] (January 1948), Retrieved 28 November 2010</ref><ref>{{cite journal|last1=Street|first1=K.|last2=Ghiorso|first2=A.|last3=Seaborg|first3=G.|title=The Isotopes of Americium|doi=10.1103/PhysRev.79.530|year=1950|page=530|volume=79|journal=Physical Review|url=http://repositories.cdlib.org/cgi/viewcontent.cgi?article=7073&context=lbnl|issue=3|bibcode = 1950PhRv...79..530S }}</ref><ref name="g1252">Greenwood, p. 1252</ref>
| | 、グランビルの天軍が最も鮮やかに表示されます。 神はクラッシュを横に振ったと彼自身と宇宙全体、他の動きを分離、独自のコンセプトを置くことができ、刻ま<br>Fanghan李は彼自身を感じ、世界のすべての接触を遮断した,[http://www.aseanacity.com/webalizer/prada-bags-34.html プラダ 長財布]。<br>ようなワンヤン神のような他のマスター、、紅海Mozunのためならば、このトリックは長い間抵抗することである,[http://www.aseanacity.com/webalizer/prada-bags-32.html プラダ ピンク 財布]。 ああ<br>,[http://www.aseanacity.com/webalizer/prada-bags-27.html プラダ 財布 値段]！ ドラゴンドラゴンは彼の手は一つの世界、竜界、仏教界、霊界を果たしなっ吹いたすべて一緒コミュニティ全体として<br>側風邪喉が、叫びに勃発した,[http://www.aseanacity.com/webalizer/prada-bags-22.html プラダ メンズ ベルト].......<br>、各空、あらゆる衝撃に対する冷たい側面衝突拳は天と地のための再誘導を試みて、力を戦って3回を費やしている '私は、私は、私は宇宙が......統一天と地を作成し、私は時代を変換し、世界を創造文明を作成した」撃たパンチ、両方ワンの円は、天が打ち砕かれた、空が崩壊しなければならない沈む,[http://www.aseanacity.com/webalizer/prada-bags-32.html プラダ 財布 リボン]。 顔が動かない<br>Huangfu海岸、張石の変更、オリバー |
| | | 相关的主题文章： |
| The new element was isolated from its [[oxide]]s in a complex, multi-step process. First [[plutonium]]-239 nitrate (<sup>239</sup>PuNO<sub>3</sub>) solution was coated on a [[platinum]] foil of about 0.5 cm<sup>2</sup> area, the solution was evaporated and the residue was converted into plutonium dioxide (PuO<sub>2</sub>) by annealing. After cyclotron irradiation, the coating was dissolved with [[nitric acid]], and then precipitated as the hydroxide using concentrated aqueous [[ammonium hydroxide|ammonia solution]]. The residue was dissolved in [[perchloric acid]]. Further separation was carried out by [[ion exchange]], yielding a certain isotope of curium. The separation of curium and americium was so painstaking that those elements were initially called by the Berkeley group as ''[[wikt:pandemonium|pandemonium]]'' (from Greek for ''all demons'' or ''hell'') and ''[[wikt:delirium|delirium]]'' (from Latin for ''madness'').<ref name=radio/><ref>{{cite book| author = Robert E. Krebs| title = The History and Use of Our Earth's Chemical Elements: A Reference Guide, Second Edition| url = http://books.google.com/?id=yb9xTj72vNAC&pg=PA322| year = 2006| publisher = Greenwood Publishing Group| isbn = 978-0-313-33438-2| page = 322 }}</ref><ref>{{OEtymD|pandemonium}}</ref><ref>{{OEtymD|delirium}}</ref>
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| Initial experiments yielded four americium isotopes: <sup>241</sup>Am, <sup>242</sup>Am, <sup>239</sup>Am and <sup>238</sup>Am. [[Americium-241]] was directly obtained from plutonium upon absorption of one neutron. It decays by emission of a [[alpha particle|α-particle]] to <sup>237</sup>Np; the [[half-life]] of this decay was first determined as 510 ± 20 years but then corrected to 432.2 years.<ref name="nubase">{{cite journal|last1=Audi|first1=G|doi=10.1016/S0375-9474(97)00482-X|title=The N? evaluation of nuclear and decay properties|year=1997|page=1|volume=624|journal=Nuclear Physics A|url=http://www.nndc.bnl.gov/amdc/nubase/Nubase2003.pdf|bibcode=1997NuPhA.624....1A|last2=Bersillon|first2=O.|last3=Blachot|first3=J.|last4=Wapstra|first4=A.H.}}</ref>
| | <li>[http://goobike.com/cgi-bin/search/zaiko_bike.cgi 「牙は肉道路から派生3スケルトンに直面しているコールド]</li> |
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| :<math>\mathrm{^{239}_{\ 94}Pu\ \xrightarrow {(n,\gamma)} \ ^{240}_{\ 94}Pu\ \xrightarrow {(n,\gamma)} \ ^{241}_{\ 94}Pu\ \xrightarrow [14.35 \ yr]{\beta^-} \ ^{241}_{\ 95}Am\ \left(\ \xrightarrow [432.2 \ yr]{\alpha} \ ^{237}_{\ 93}Np \right)}</math>
| | <li>[http://www.cooncat.net/cgi-bin/guestbook/guestbook.cgi 十分な運動量は、全体の公正なリターンを破壊してきた]</li> |
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| : <small> The times are [[half-life|half-lives]]</small>
| | <li>[http://jianbowang.net/plus/feedback.php?aid=14 脱出を免れることはできない]</li> |
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| The second isotope <sup>242</sup>Am was produced upon neutron bombardment of the already-created <sup>241</sup>Am. Upon rapid [[Beta-decay|β-decay]], <sup>242</sup>Am converts into the isotope of curium <sup>242</sup>Cm (which had been discovered previously). The half-life of this decay was initially determined at 17 hours, which was close to the presently accepted value of 16.02 h.<ref name="nubase"/>
| | </ul> |
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| : <math>\mathrm{^{241}_{\ 95}Am\ \xrightarrow {(n,\gamma)} \ ^{242}_{\ 95}Am\ \left(\ \xrightarrow [16.02 \ h]{\beta^-} \ ^{242}_{\ 96}Cm \right)}</math>
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| The discovery of americium and curium in 1944 was closely related to the [[Manhattan Project]]; the results were confidential and declassified only in 1945. Seaborg leaked the synthesis of the elements 95 and 96 on the U.S. radio show for children, the [[Quiz Kids]], five days before the official presentation at an [[American Chemical Society]] meeting on 11 November 1945, when one of the listeners asked whether any new transuranium element beside plutonium and neptunium had been discovered during the war.<ref name="radio">{{cite web|url = http://pubs.acs.org/cen/80th/americium.html|title = Chemical & Engineering News: It's Elemental: The Periodic Table – Americium|accessdate =7 July 2010| first = Rachel Sheremeta|last = Pepling|year = 2003}}</ref> After the discovery of americium isotopes <sup>241</sup>Am and <sup>242</sup>Am, their production and compounds were patented listing only Seaborg as the inventor.<ref>Seaborg, Glenn T. {{US patent|3156523}} "Element", Filing date: 23 August 1946, Issue date: 10 November 1964</ref> The initial americium samples weighed a few micrograms; they were barely visible and were identified by their radioactivity. The first substantial amounts of metallic americium weighing 40–200 micrograms were not prepared until 1951 by reduction of [[americium(III) fluoride]] with [[barium]] metal in high vacuum at 1100 °C.<ref name="AM_METALL1">{{cite journal|last1=Westrum|first1=Edgar F.|last2=Eyring|first2=Leroy|journal=Journal of the American Chemical Society|volume=73|page=3396|year=1951|doi=10.1021/ja01151a116|issue=7}}</ref>
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| ==Occurrence==
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| {{See also|Nuclear reprocessing}}
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| [[File:Ivy Mike - mushroom cloud.jpg|thumb|Americium was detected in the fallout from the ''Ivy Mike'' nuclear test.]]
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| The longest-lived and most common isotopes of americium, <sup>241</sup>Am and <sup>243</sup>Am, have half-lives of 432.2 and 7,370 years, respectively. Therefore, all [[Primordial nuclide|primordial]] americium (americium that was present on Earth during its formation) should have decayed by now.
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| Existing americium is concentrated in the areas used for the atmospheric [[nuclear weapons testing|nuclear weapons tests]] conducted between 1945 and 1980, as well as at the sites of nuclear incidents, such as the [[Chernobyl disaster]]. For example, the analysis of the debris at the testing site of the first U.S. [[hydrogen bomb]], [[Ivy Mike]], (1 November 1952, [[Enewetak Atoll]]), revealed high concentrations of various actinides including americium; due to military secrecy, this result was published only in 1956.<ref>{{cite journal|last1=Fields|first1=P. R.|last2=Studier|first2=M. H.|last3=Diamond|first3=H.|last4=Mech|first4=J. F.|last5=Inghram|first5=M. G.|last6=Pyle|first6=G. L.|last7=Stevens|first7=C. M.|last8=Fried|first8=S.|last9=Manning|first9=W. M.|last10=Ghiorso|first10=A.|last11=Thompson|first11=S. G.|last12=Higgins|first12=G. H.|last13=Seaborg|first13=G. T.|displayauthors=3|title=Transplutonium Elements in Thermonuclear Test Debris|year=1956|journal=Physical Review|volume=102|issue=1|pages=180–182|doi=10.1103/PhysRev.102.180|bibcode=1956PhRv..102..180F}}</ref> [[Trinitite]], the glassy residue left on the desert floor near [[Alamogordo]], [[New Mexico]], after the [[plutonium]]-based [[Trinity test|Trinity]] [[nuclear testing|nuclear bomb test]] on 16 July 1945, contains traces of americium-241. Elevated levels of americium were also detected at the [[1968 Thule Air Base B-52 crash|crash site]] of a US B-52 bomber, which carried four hydrogen bombs, in 1968 in [[Greenland]].<ref>{{cite book|author=Eriksson, Mats|title=On Weapons Plutonium in the Arctic Environment|publisher=[[Lund University]]|date=April 2002|location=Risø National Laboratory, Roskilde, Denmark|accessdate=15 November 2008|url=http://www.risoe.dk/rispubl/NUK/nukpdf/ris-r-1321.pdf|format=PDF|page=28| archiveurl= http://web.archive.org/web/20081218233551/http://www.risoe.dk/rispubl/NUK/nukpdf/ris-r-1321.pdf| archivedate= 18 December 2008| deadurl= no}}</ref>
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| In other regions, the average radioactivity of surface soil due to residual americium is only about 0.01 [[Curie|picocuries]]/g (0.37 [[Becquerel|mBq]]/g). Atmospheric americium compounds are poorly soluble in common solvents and mostly adhere to soil particles. Soil analysis revealed about 1,900 times higher concentration of americium inside sandy soil particles than in the water present in the soil pores; an even higher ratio was measured in [[loam]] soils.<ref name="am">[http://www.ead.anl.gov/pub/doc/americium.pdf Human Health Fact Sheet on Americium], Los Alamos National Laboratory, Retrieved 28 November 2010</ref>
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| Americium is produced mostly artificially in small quantities, for research purposes. A tonne of spent nuclear fuel contains about 100 grams of various americium isotopes, mostly <sup>241</sup>Am and <sup>243</sup>Am.<ref>Hoffmann, Klaus ''Kann man Gold machen? Gauner, Gaukler und Gelehrte. Aus der Geschichte der chemischen Elemente'' (Can you make gold? Crooks, clowns and scholars. From the history of the chemical elements), Urania-Verlag, Leipzig, Jena, Berlin 1979, no ISBN, p. 233</ref> Their prolonged radioactivity is undesirable for the disposal, and therefore americium, together with other long-lived actinides, have to be neutralized. The associated procedure may involve several steps, where americium is first separated and then converted by neutron bombardment in special reactors to short-lived nuclides. This procedure is well known as [[nuclear transmutation]], but it is still being developed for americium.<ref>Baetslé, L. [http://www.ictp.trieste.it/~pub_off/lectures/lns012/Baetsle.pdf Application of Partitioning/Transmutation of Radioactive Materials in Radioactive Waste Management], Nuclear Research Centre of Belgium Sck/Cen, Mol, Belgium, September 2001, Retrieved 28 November 2010</ref><ref>Fioni, Gabriele; Cribier, Michel and Marie, Frédéric [http://www.cea.fr/var/cea/storage/static/gb/library/Clefs46/pagesg/clefs46_30.html Can the minor actinide, americium-241, be transmuted by thermal neutrons?], Department of Astrophysics, CEA/Saclay, Retrieved 28 November 2010</ref>
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| A few atoms of americium can be produced by [[Neutron capture|neutron capture reactions]] and [[beta decay]] in very highly concentrated [[uranium]]-bearing deposits.<ref name="emsley">{{cite book| last = Emsley| first = John| title = Nature's Building Blocks: An A-Z Guide to the Elements| edition = New| year = 2011| publisher = Oxford University Press| location = New York, NY| isbn = 978-0-19-960563-7 }}</ref>
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| ==Synthesis and extraction==
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| ===Isotope nucleosyntheses===
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| [[File:Elutionskurven Tb Gd Eu und Bk Cm Am.png|thumb|[[Chromatography|Chromatographic]] [[elution]] curves revealing the similarity between the lanthanides Tb, Gd, and Eu and the corresponding actinides Bk, Cm, and Am.]]
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| Americium has been produced in small quantities in [[nuclear reactor]]s for decades, and kilograms of its <sup>241</sup>Am and <sup>243</sup>Am isotopes have been accumulated by now.<ref name="g1262">Greenwood, p. 1262</ref> Nevertheless, since it was first offered for sale in 1962, its price, about 1,500 [[United States dollar|USD]] per gram of <sup>241</sup>Am, remains almost unchanged owing to the very complex separation procedure.<ref name="smoke">[http://www.world-nuclear.org/info/inf57.html Smoke detectors and americium], World Nuclear Association, January 2009, Retrieved 28 November 2010</ref> The heavier isotope <sup>243</sup>Am is produced in much smaller amounts; it is thus more difficult to separate, resulting in a higher cost of the order 100,000–160,000 USD/g.<ref name="CRC">Hammond C. R. "The elements" in {{RubberBible86th}}</ref><ref>{{cite book| author = H. J. Emeleus| coauthors = A. G. Sharpe| title = Advances in Inorganic Chemistry | url = http://books.google.com/?id=K5_LSQqeZ_IC&pg=PA2| year = 1987| publisher = Academic Press| isbn = 978-0-08-057880-4| page = 2 }}</ref>
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| Americium is not synthesized directly from uranium – the most common reactor material – but from the plutonium isotope <sup>239</sup>Pu. The latter needs to be produced first, according to the following nuclear process:
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| : <math>\mathrm{^{238}_{\ 92}U\ \xrightarrow {(n,\gamma)} \ ^{239}_{\ 92}U\ \xrightarrow [23.5 \ min]{\beta^-} \ ^{239}_{\ 93}Np\ \xrightarrow [2.3565 \ d]{\beta^-} \ ^{239}_{\ 94}Pu}</math>
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| The capture of two neutrons by <sup>239</sup>Pu (a so-called (n,γ) reaction), followed by a β-decay, results in <sup>241</sup>Am:
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| : <math>\mathrm{^{239}_{\ 94}Pu\ \xrightarrow {2(n,\gamma)} \ ^{241}_{\ 94}Pu\ \xrightarrow [14.35 \ yr]{\beta^-} \ ^{241}_{\ 95}Am}</math>
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| The plutonium present in spent nuclear fuel contains about 12% of <sup>241</sup>Pu. Because it spontaneously converts to <sup>241</sup>Am, <sup>241</sup>Pu can be extracted and may be used to generate further <sup>241</sup>Am.<ref name="smoke"/> However, this process is rather slow: half of the original amount of <sup>241</sup>Pu decays to <sup>241</sup>Am after about 15 years, and the <sup>241</sup>Am amount reaches a maximum after 70 years.<ref>[http://www.bredl.org/sapc/Pu_ReportI.htm BREDL Southern Anti-Plutonium Campaign], Blue Ridge Environmental Defense League, Retrieved 28 November 2010</ref>
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| The obtained <sup>241</sup>Am can be used for generating heavier americium isotopes by further neutron capture inside a nuclear reactor. In a [[light water reactor]] (LWR), 79% of <sup>241</sup>Am converts to <sup>242</sup>Am and 10% to its [[nuclear isomer]] <sup>242m</sup>Am:<ref group=note>The "metastable" state is marked by the letter m.</ref><ref>{{cite journal|doi=10.3327/jnst.41.448|author=Sasahara, A. ''et al.''|title=Neutron and Gamma Ray Source Evaluation of LWR High Burn-up UO<sub>2</sub> and MOX Spent Fuels|journal=Journal of Nuclear Science and Technology|year=2004|volume=41|issue=4|pages=448–456|url=http://www.jstage.jst.go.jp/article/jnst/41/4/448/_pdf}} [http://sciencelinks.jp/j-east/ article/200410/000020041004A0333355.php Abstract]</ref>
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| :79%: <math>\mathrm{^{241}_{\ 95}Am\ \xrightarrow {(n,\gamma)} \ ^{242}_{\ 95}Am}</math>
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| :10%: <math>\mathrm{^{241}_{\ 95}Am\ \xrightarrow {(n,\gamma)} \ ^{242m}_{\ \ \ 95}Am}</math>
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| [[Americium-242]] has a half-life of only 16 hours, which makes its further up-conversion to <sup>243</sup>Am, extremely inefficient. The latter isotope is produced instead in a process where <sup>239</sup>Pu captures four neutrons under high [[neutron flux]]:
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| : <math>\mathrm{^{239}_{\ 94}Pu\ \xrightarrow {4(n,\gamma)} \ ^{243}_{\ 94}Pu\ \xrightarrow [4.956 \ h]{\beta^-} \ ^{243}_{\ 95}Am}</math>
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| === Metal generation ===
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| Most synthesis routines yield a mixture of different actinide isotopes in oxide forms, from which isotopes of americium need to be separated. In a typical procedure, the spent reactor fuel (e.g. [[MOX fuel]]) is dissolved in [[nitric acid]], and the bulk of uranium and plutonium is removed using a [[PUREX]]-type extraction ('''P'''lutonium –'''UR'''anium '''EX'''traction) with [[tributyl phosphate]] in a [[hydrocarbon]]. The lanthanides and remaining actinides are then separated from the aqueous residue ([[raffinate]]) by a [[diamide]]-based extraction, to give, after stripping, a mixture of trivalent actinides and lanthanides. Americium compounds are then selectively extracted using multi-step [[chromatography|chromatographic]] and centrifugation techniques<ref>Penneman, pp. 34–48</ref> with an appropriate reagent. A large amount of work has been done on the [[solvent extraction]] of americium. For example, a recent [[European Union|EU]] funded project codenamed "EUROPART" studied [[triazine]]s and other compounds as potential extraction agents.<ref>{{cite journal|journal = [[Dalton Trans.]]|year = 2003|pages = 1675–1685|doi = 10.1039/b301178j|title = The coordination chemistry of 1,2,4-triazinyl bipyridines with lanthanide(III) elements – implications for the partitioning of americium(III)|author = Hudson, M. J. ''et al.''|issue = 9}}</ref><ref>{{cite web|author = Geist, A. '' et al.''|title= Actinide(III)/Lanthanide(III) Partitioning Using n-Pr-BTP as Extractant: Extraction Kinetics and Extraction Test in a Hollow Fiber Module|work = 6th Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation|publisher = [[OECD Nuclear Energy Agency]]|date = 11–13 December 2000|url = http://www.nea.fr/html/pt/docs/iem/madrid00/Paper14.pdf|format=PDF}}</ref><ref>{{cite web|url = http://www-atalante2004.cea.fr/home/liblocal/docs/atalante2000/P3-26.pdf|title = Sanex-BTP Process Development Studies|work = Atalante 2000: Scientific Research on the Back-end of the Fuel Cycle for the 21st Century|publisher = Commissariat à l'énergie atomique|date = 24–26 October 2000|author = C. Hill, D. Guillaneux, X. Hérès, N. Boubals and L. Ramain|format=PDF}}</ref><ref>{{cite web|title = Effective Actinide(III)-Lanthanide(III) Separation in Miniature Hollow Fibre Modules|author = Geist, A. ''et al.''|url =http://www.nea.fr/html/pt/docs/iem/jeju02/session2/SessionII-15.pdf|work = 7th Information Exchange Meeting on Actinide and Fission Product Partitioning and Transmutation|date = 14–16 October 2002|publisher = OECD Nuclear Energy Agency|format=PDF}}</ref><ref>{{cite web|title = Separation Studies of ''f''-Elements|author = D.D. Ensor|publisher = [[Tennessee Tech University]]|url = http://www.tntech.edu/WRC/pdfs/Projects04_05/Ens_Elem.pdf|format=PDF}}</ref> [[BTBP|''Bis''-triazinyl bipyridine]] complex has been recently proposed as such reagent as highly selective to americium (and curium).<ref>{{cite journal|author = Magnusson D, Christiansen B, Foreman MRS, Geist A, Glatz JP, Malmbeck R, Modolo G, Serrano-Purroy D and Sorel C|journal = Solvent Extraction and Ion Exchange|year = 2009|volume = 27|page = 97|doi = 10.1080/07366290802672204|title = Demonstration of a SANEX Process in [[centrifugal extractor|Centrifugal Contactors]] using the CyMe4-BTBP Molecule on a Genuine Fuel Solution|issue = 2}}</ref> Separation of americium from the highly similar curium can be achieved by treating a slurry of their hydroxides in aqueous [[sodium bicarbonate]] with [[ozone]], at elevated temperatures. Both Am and Cm are mostly present in solutions in the +3 valence state; whereas curium remains unchanged, americium oxidizes to soluble Am(IV) complexes which can be washed away.<ref>Penneman, p. 25</ref>
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| Metallic americium is obtained by [[Redox|reduction]] from its compounds. Americium(III) fluoride was first used for this purpose. The reaction was conducted using elemental [[barium]] as reducing agent in a water- and oxygen-free environment inside an apparatus made of [[tantalum]] and [[tungsten]].<ref Name="AM_METALL1"/><ref name = "Gmelin">''Gmelin Handbook of Inorganic Chemistry'', System No. 71, transuranics, Part B 1, pp. 57–67.</ref><ref name="p3">Penneman, p. 3</ref>
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| : <math>\mathrm{2\ AmF_3\ +\ 3\ Ba\ \longrightarrow \ 2\ Am\ +\ 3\ BaF_2}</math>
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| An alternative is the reduction of [[americium dioxide]] by metallic [[lanthanum]] or [[thorium]]:<ref name=p3/><ref Name="AM_METALL2"/>
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| : <math>\mathrm{3\ AmO_2\ +\ 4\ La\ \longrightarrow \ 3\ Am\ +\ 2\ La_2O_3}</math>
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| ==Physical properties==
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| [[File:Closest packing ABAC.png|thumb|Double-hexagonal close packing with the layer sequence ABAC in the crystal structure of α-americium (A: green, B: blue, C: red).]]
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| In the [[periodic table]], americium is located to the right of plutonium, to the left of curium, and below the lanthanide [[europium]], with which it shares many similarities in physical and chemical properties. Americium is a highly radioactive element. When freshly prepared, it has a silvery-white metallic lustre, but then slowly tarnishes in air. With a density of 12 g/cm<sup>3</sup>, americium is less dense than both curium (13.52 g/cm<sup>3</sup>) and plutonium (19.8 g/cm<sup>3</sup>); but has a higher density than europium (5.264 g/cm<sup>3</sup>)—mostly because of its higher atomic mass. Americium is relatively soft and easily deformable and has a significantly lower [[bulk modulus]] than the actinides before it: Th, Pa, U, Np and Pu.<ref name=pressure/> Its melting point of 1173 °C is significantly higher than that of plutonium (639 °C) and europium (826 °C), but lower than for curium (1340 °C).<ref name="AM_METALL2">{{cite journal|last1=Wade|first1=W|title=Preparation and some properties of americium metal|journal=Journal of Inorganic and Nuclear Chemistry|volume=29|page=2577|year=1967|doi=10.1016/0022-1902(67)80183-0|issue=10|last2=Wolf|first2=T.}}</ref><ref name="AM_METALL2"/><ref name="AM_METALL4"/>
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| At ambient conditions, americium is present in its most stable α form which has a [[Hexagonal crystal system|hexagonal crystal symmetry]], and a [[space group]] P6<sub>3</sub>/mmc with lattice parameters ''a'' = 346.8 [[picometer|pm]] and ''c'' = 1124 pm, and four atoms per [[unit cell]]. The crystal consists of a double-[[Close-packing of spheres|hexagonal close packing]] with the layer sequence ABAC and so is isotypic with α-lanthanum and several actinides such as α-curium.<ref name="Gmelin"/><ref name = "AM_METALL4">{{cite journal|last1=McWhan|first1=D.B.|last2=Cunningham|first2=B.B.|last3=Wallmann|first3=J.C.|title=Crystal structure, thermal expansion and melting point of americium metal|journal=Journal of Inorganic and Nuclear Chemistry|volume=24|page=1025|year=1962|doi=10.1016/0022-1902(62)80246-2|issue=9}}</ref> The crystal structure of americium changes with pressure and temperature. When compressed at room temperature to 5 GPa, α-Am transforms to the β modification, which has a [[Cubic crystal system|face-centered cubic]] (''fcc'') symmetry, space group Fm{{overline|3}}m and lattice constant ''a'' = 489 pm. This ''fcc'' structure is equivalent to the closest packing with the sequence ABC.<ref name="Gmelin"/><ref name = "AM_METALL4"/> Upon further compression to 23 GPa, americium transforms to an [[Orthorhombic crystal system|orthorhombic]] γ-Am structure similar to that of α-uranium. There are no further transitions observed up to 52 GPa, except for an appearance of a monoclinic phase at pressures between 10 and 15 GPa.<ref name="pressure">{{cite journal|last1=Benedict|first1=U|title=Study of actinide metals and actinide compounds under high pressures|journal=Journal of the Less Common Metals|volume=100|page=153|year=1984|doi=10.1016/0022-5088(84)90061-4}}</ref> There is no consistency on the status of this phase in the literature, which also sometimes lists the α, β and γ phases as I, II and III. The β-γ transition is accompanied by a 6% decrease in the crystal volume; although theory also predicts a significant volume change for the α-β transition, it is not observed experimentally. The pressure of the α-β transition decreases with increasing temperature, and when α-americium is heated at ambient pressure, at 770 °C it changes into an ''fcc'' phase which is different from β-Am, and at 1075 °C it converts to a [[Cubic crystal system|body-centered cubic]] structure. The pressure-temperature phase diagram of americium is thus rather similar to those of lanthanum, [[praseodymium]] and [[neodymium]].<ref>{{cite book| author = D. A. Young| title = Phase diagrams of the elements| url = http://books.google.com/?id=F2HVYh6wLBcC&pg=PA226| year = 1991| publisher = University of California Press| isbn = 978-0-520-91148-2| page = 226 }}</ref>
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| As with many other actinides, self-damage of the crystal lattice due to alpha-particle irradiation is intrinsic to americium. It is especially noticeable at low temperatures, where the mobility of the produced [[Interstitial defect|lattice defects]] is relatively low, by broadening of [[X-ray diffraction]] peaks. This effect makes somewhat uncertain the temperature of americium and some of its properties, such as electrical [[resistivity]].<ref>{{cite journal|last1=Benedict|first1=U|last2=Dufour|first2=C|title=Low temperature lattice expansion of americium dioxide|journal=Physica B+C|volume=102|page=303|year=1980|doi=10.1016/0378-4363(80)90178-3|bibcode = 1980PhyBC.102..303B }}</ref> So for americium-241, the resistivity at 4.2 K increases with time from about 2 µOhm·cm to 10 µOhm·cm after 40 hours, and saturates at about 16 µOhm·cm after 140 hours. This effect is less pronounced at room temperature, due to annihilation of radiation defects; also heating to room temperature the sample which was kept for hours at low temperatures restores its resistivity. In fresh samples, the resistivity gradually increases with temperature from about 2 µOhm·cm at [[liquid helium]] to 69 µOhm·cm at room temperature; this behavior is similar to that of neptunium, uranium, thorium and [[protactinium]], but is different from plutonium and curium which show a rapid rise up to 60 K followed by saturation. The room temperature value for americium is lower than that of neptunium, plutonium and curium, but higher than for uranium, thorium and protactinium.<ref name=res/>
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| Americium is [[paramagnetism|paramagnetic]] in a wide temperature range, from that of [[liquid helium]], to room temperature, and above. This behavior is markedly different from that of its neighbor curium which exhibit antiferromagnetic transition at 52 K.<ref>{{cite journal|last1=Kanellakopulos|first1=B|title=The magnetic susceptibility of Americium and curium metal|journal=Solid State Communications|volume=17|page=713|year=1975|doi=10.1016/0038-1098(75)90392-0|issue=6|bibcode = 1975SSCom..17..713K|last2=Blaise|first2=A.|last3=Fournier|first3=J.M.|last4=Müller|first4=W. }}</ref> The [[thermal expansion]] coefficient of americium is slightly anisotropic and amounts to (7.5 ± 0.2){{e|-6}}/°C along the shorter ''a'' axis and (6.2 ± 0.4){{e|-6}}/°C for the longer ''c'' hexagonal axis.<ref name = "AM_METALL4"/> The [[Enthalpy change of solution|enthalpy of dissolution]] of americium metal in [[hydrochloric acid]] at standard conditions is −620.6 ± 1.3 kJ/mol, from which the [[Standard enthalpy change of formation (data table)|standard enthalpy change of formation]] (Δ<sub>f</sub>''H''°) of aqueous Am<sup>3+</sup> ion is −621.2 ± 2.0 kJ/mol<sup>−1</sup>. The [[standard potential]] Am<sup>3+</sup>/Am<sup>0</sup> is 2.08 ± 0.01 V.<ref>{{cite journal|last1=Mondal|first1=J.U.|last2=Raschella|first2=D.L.|last3=Haire|first3=R.G.|last4=Petereson|first4=J.R.|title=The enthalpy of solution of 243Am metal and the standard enthalpy of formation of Am3+(aq)|journal=Thermochimica Acta|volume=116|page=235|year=1987|doi=10.1016/0040-6031(87)88183-2}}</ref>
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| ==Chemical properties==
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| [[File:Americium34.jpg|thumb|Americium ions in solution: Am<sup>3+</sup> (left) and Am<sup>4+</sup> (right). Am<sup>3+</sup> is colorless at low and reddish at higher concentrations.]]
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| Americium readily reacts with oxygen and dissolves well in [[acid]]s. The most common [[oxidation state]] for americium is +3,<ref name="p4">Penneman, p. 4</ref> in which americium compounds are rather stable against oxidation and reduction. In this sense, americium is chemically similar to most lanthanides. The trivalent americium forms insoluble [[fluoride]], [[oxalate]], [[iodate]], [[hydroxide]], [[phosphate]] and other salts.<ref name=p4/> Other oxidation states have been observed between +2 and +7, which is the widest range among the actinide elements. Their color in aqueous solutions varies as follows: Am<sup>3+</sup> (colorless to yellow-reddish), Am<sup>4+</sup> (yellow-reddish), Am<sup>V</sup>{{chem|O|2|+}}; (yellow), Am<sup>VI</sup>{{chem|O|2|2+}} (brown) and Am<sup>VII</sup>{{chem|O|6|5-}} (dark green).<ref>[http://www.chemie-master.de/FrameHandler.php?loc=http://www.chemie-master.de/pse/pse.php?modul=Am Americium], Das Periodensystem der Elemente für den Schulgebrauch (The periodic table of elements for schools) chemie-master.de (in German), Retrieved 28 November 2010</ref><ref name="g1265">Greenwood, p. 1265</ref> All oxidation states have their characteristic optical absorption spectra, with a few sharp peaks in the visible and mid-infrared regions, and the position and intensity of these peaks can be converted into the concentrations of the corresponding oxidation states.<ref>Penneman, pp. 10–14</ref><ref name=amoh4/><ref name=carbonate/> For example, Am(III) has two sharp peaks at 504 and 811 nm, Am(V) at 514 and 715 nm, and Am(VI) at 666 and 992 nm.<ref name=haxav/>
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| Americium compounds with oxidation state +4 and higher are strong oxidizing agents, comparable in strength to the [[permanganate]] ion ({{chem|MnO|4|-}}) in acidic solutions.<ref name = "HOWI_1956">Holleman, p. 1956</ref> Whereas the Am<sup>4+</sup> ions are unstable in solutions and readily convert to Am<sup>3+</sup>, the +4 oxidation state occurs well in solids, such as [[americium dioxide]] (AmO<sub>2</sub>) and americium(IV) fluoride (AmF<sub>4</sub>).
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| All [[pentavalent]] and [[hexavalent]] americium compounds are complex salts such as KAmO<sub>2</sub>F<sub>2</sub>, Li<sub>3</sub>AmO<sub>4</sub> and Li<sub>6</sub>AmO<sub>6</sub>, Ba<sub>3</sub>AmO<sub>6</sub>, AmO<sub>2</sub>F<sub>2</sub>. These high oxidation states Am(IV), Am(V) and Am(VI) can be prepared from Am(III) by oxidation with [[ammonium persulfate]] in dilute nitric acid,<ref>{{cite journal|last1=Asprey|first1=L. B.|last2=Stephanou|first2=S. E.|last3=Penneman|first3=R. A.|journal=Journal of the American Chemical Society|volume=72|page=1425|year=1950|doi=10.1021/ja01159a528|issue=3}}</ref> with [[Silver oxide|silver(I) oxide]] in [[perchloric acid]],<ref name="haxav">{{cite journal|last1=Asprey|first1=L. B.|last2=Stephanou|first2=S. E.|last3=Penneman|first3=R. A.|title=Hexavalent Americium|journal=Journal of the American Chemical Society|volume=73|page=5715|year=1951|doi=10.1021/ja01156a065|issue=12}}</ref> or with [[ozone]] or [[sodium persulfate]] in [[sodium carbonate]] solutions.<ref name="carbonate">{{cite journal|last1=Coleman|first1=J. S.|last2=Keenan|first2=T. K.|last3=Jones|first3=L. H.|last4=Carnall|first4=W. T.|last5=Penneman|first5=R. A.|title=Preparation and Properties of Americium(VI) in Aqueous Carbonate Solutions|journal=Inorganic Chemistry|volume=2|page=58|year=1963|doi=10.1021/ic50005a017}}</ref> The pentavalent oxidation state of americium was first observed in 1951.<ref>{{cite journal|last1=Werner|first1=L. B.|last2=Perlman|first2=I.|journal=Journal of the American Chemical Society|volume=73|page=495|year=1951|doi=10.1021/ja01145a540}}</ref> It is present in aqueous solution in the form of {{chem|AmO|2|+}} ions (acidic) or {{chem|AmO|3|-}} ions (alkaline) which are however unstable and subject to several rapid [[disproportionation]] reactions:<ref>{{cite journal|last1=Hall|first1=G|title=The self-reduction of americium(V) and (VI) and the disproportionation of americium(V) in aqueous solution|journal=Journal of Inorganic and Nuclear Chemistry|volume=4|page=296|year=1957|doi=10.1016/0022-1902(57)80011-6|issue=5–6|last2=Markin|first2=T.L.}}</ref><ref>{{cite journal|last1=Coleman|first1=James S.|title=The Kinetics of the Disproportionation of Americium(V)|journal=Inorganic Chemistry|volume=2|page=53|year=1963|doi=10.1021/ic50005a016}}</ref><ref name="g1275">Greenwood, p. 1275</ref>
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| : <math>\mathrm{3\ AmO_2^+\ +\ 4\ H^+\ \longrightarrow \ 2\ AmO_2^{2+}\ +\ Am^{3+}\ +\ 2\ H_2O}</math>
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| : <math>\mathrm{2\ Am (V)\ \longrightarrow \ Am (VI)\ +\ Am (IV)}</math>
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| ==Chemical compounds==
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| ===Oxygen compounds===
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| Two americium oxides are known, with the oxidation states +3 (Am<sub>2</sub>O<sub>3</sub>) and +4 (AmO<sub>2</sub>). [[Americium(III) oxide]] is a red-brown solid with a melting point of 2205 °C.<ref name = "HOWI_1972">Holleman, p. 1972</ref> [[Americium dioxide|Americium(IV) oxide]] is the main form of solid americium which is used in nearly all its applications. As most other actinide dioxides, it is a black solid with a cubic ([[fluorite]]) crystal structure.<ref name="g1267">Greenwood, p. 1267</ref>
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| The oxalate of americium(III), vacuum dried at room temperature, has the chemical formula Am<sub>2</sub>(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>·7H<sub>2</sub>O. Upon heating in vacuum, it loses water at 240 °C and starts decomposing into AmO<sub>2</sub> at 300 °C, the decomposition completes at about 470 °C.<ref name=p4/> The initial oxalate dissolves in nitric acid with the maximum solubility of 0.25 g/L.<ref name="p5">Penneman, p. 5</ref>
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| ===Halides===
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| [[Halide]]s of americium are known for the oxidation states +2, +3 and +4,<ref name="HOWI_1969">Holleman, p. 1969</ref> where the +3 is most stable, especially in solutions.<ref name="hal1">{{cite journal|last1=Asprey|first1=L. B.|last2=Keenan|first2=T. K.|last3=Kruse|first3=F. H.|journal=Inorganic Chemistry|volume=4|page=985|year=1965|doi=10.1021/ic50029a013|issue=7}}</ref>
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| {| Class ="wikitable" style ="text-align:center;"
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| |-
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| ! Oxidation state
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| ! F
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| ! Cl
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| ! Br
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| ! I
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| |-
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| ! +4
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| | [[Americium(IV) fluoride]] <br /> AmF<sub>4</sub><br /> pale pink
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| |-
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| ! +3
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| | [[Americium(III) fluoride]] <br /> AmF<sub>3</sub><br /> pink
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| | [[Americium(III) chloride]] <br /> AmCl<sub>3</sub><br /> pink
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| | [[Americium(III) bromide]] <br /> AmBr<sub>3</sub><br /> light yellow
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| | [[Americium(III) iodide]] <br /> AmI<sub>3</sub><br /> light yellow
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| |-
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| ! +2
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| | [[Americium(II) chloride]] <br /> AmCl<sub>2</sub><br /> black <!-- (CAS: 16601-54-0) --->
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| | [[Americium(II) bromide]] <br /> AmBr<sub>2</sub><br /> black <!-- (CAS: 39705-49-2) -->
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| | [[Americium(II) iodide]] <br /> AmI<sub>2</sub><br /> black <!-- (CAS: 38150-40-2) -->
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| |}
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| Reduction of Am(III) compounds with sodium [[Amalgam (chemistry)|amalgam]] yields Am(II) salts – the black halides AmCl<sub>2</sub>, AmBr<sub>2</sub> and AmI<sub>2</sub>. They are very sensitive to oxygen and oxidize in water, releasing hydrogen and converting back to the Am(III) state. Specific lattice constants are:
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| * [[Orthorhombic crystal system|Orthorhombic]] AmCl<sub>2</sub>: ''a'' = 896.3 ± 0.8 pm, ''b'' = 757.3 ± 0.8 pm and ''c'' = 453.2 ± 0.6 pm
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| * [[Tetragonal crystal system|Tetragonal]] AmBr<sub>2</sub>: ''a'' = 1159.2 ± 0.4 and ''c'' = 712.1 ± 0.3 pm.<ref>{{cite journal|last1=Baybarz|first1=R.D.|title=The preparation and crystal structures of americium dichloride and dibromide|journal=Journal of Inorganic and Nuclear Chemistry|volume=35|page=483|year=1973|doi=10.1016/0022-1902(73)80560-3|issue=2}}</ref>
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| They can also be prepared by reacting metallic americium with an appropriate mercury halide HgX<sub>2</sub>, where X = Cl, Br or I:<ref name="g1272">Greenwood, p. 1272</ref>
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| : <math>\mathrm{\ Am\ +\ HgX_2\ \xrightarrow {400 - 500 ^\circ C} \ AmX_2\ + \ Hg \ }</math>
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| Americium(III) fluoride (AmF<sub>3</sub>) is poorly soluble and precipitates upon reaction of Am<sup>3+</sup> and fluoride ions in weak acidic solutions:
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| : <math>\mathrm{Am^{3+}\ _{(aq)} +\ 3\ F^-\ _{(aq)} \longrightarrow \ AmF_3\ _{(s)} \downarrow}</math>
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| The tetravalent americium(IV) fluoride (AmF<sub>4</sub>) is obtained by reacting solid americium(III) fluoride with molecular [[fluorine]]:<ref name="f4">{{cite journal|last1=Asprey|first1=L. B.|journal=Journal of the American Chemical Society|volume=76|page=2019|year=1954|doi=10.1021/ja01636a094|issue=7}}</ref><ref name="g1271">Greenwood, p. 1271</ref>
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| : <math>\mathrm{2\ AmF_3\ +\ F_2\ \longrightarrow\ 2\ AmF_4}</math>
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| Another known form of solid tetravalent americium chloride is KAmF<sub>5</sub>.<ref name=f4/><ref name="p6">Penneman, p. 6</ref> Tetravalent americium has also been observed in the aqueous phase. For this purpose, black Am(OH)<sub>4</sub> was dissolved in 15-[[Mole (unit)|M]] NH<sub>3</sub>F with the americium concentration of 0.01 M. The resulting reddish solution had a characteristic optical absorption spectrum which is similar to that of AmF<sub>4</sub> but differed from other oxidation states of americium. Heating the Am(IV) solution to 90 °C did not result in its disproportionation or reduction, however a slow reduction was observed to Am(III) and assigned to self-irradiation of americium by alpha particles.<ref name="amoh4">{{cite journal|last1=Asprey|first1=L. B.|last2=Penneman|first2=R. A.|journal=Journal of the American Chemical Society|volume=83|page=2200|year=1961|doi=10.1021/ja01470a040|issue=9}}</ref>
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| Most americium(III) halides form hexagonal crystals with slight variation of the color and exact structure between the halogens. So, chloride (AmCl<sub>3</sub>) is reddish and has a structure isotypic to [[uranium(III) chloride]] (space group P6<sub>3</sub>/m) and the melting point of 715 °C.<ref name="HOWI_1969"/> The fluoride is isotypic to LaF<sub>3</sub> (space group P6<sub>3</sub>/mmc) and the iodide to BiI<sub>3</sub> (space group R{{overline|3}}). The bromide is an exception with the orthorhombic PuBr<sub>3</sub>-type structure and space group Cmcm.<ref name=hal1/> Crystals of americium hexahydrate (AmCl<sub>3</sub>·6H<sub>2</sub>O) can be prepared by dissolving americium dioxide in hydrochloric acid and evaporating the liquid. Those crystals are hygroscopic and have yellow-reddish color and a [[Monoclinic crystal system|monoclinic]] crystal structure.<ref>{{cite journal|last1=Burns|first1=John H.|last2=Peterson|first2=Joseph Richard|title=Crystal structures of americium trichloride hexahydrate and berkelium trichloride hexahydrate|journal=Inorganic Chemistry|volume=10|page=147|year=1971|doi=10.1021/ic50095a029}}</ref>
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| Oxyhalides of americium in the form Am<sup>VI</sup>O<sub>2</sub>X<sub>2</sub>, Am<sup>V</sup>O<sub>2</sub>X, Am<sup>IV</sup>OX<sub>2</sub> and Am<sup>III</sup>OX can be obtained by reacting the corresponding americium halide with oxygen or Sb<sub>2</sub>O<sub>3</sub>, and AmOCl can also be produced by vapor phase [[hydrolysis]]:<ref name=g1272/>
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| : <math>\mathrm{AmCl_3\ +\ \ H_2O\ \longrightarrow \ AmOCl\ +\ 2\ HCl}</math>
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| ===Chalcogenides and pnictides===
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| The known [[chalcogenide]]s of americium include the [[sulfide]] AmS<sub>2</sub>,<ref name="AM_S_SE">{{cite journal|last1=Damien|first1=D|title=Americium disulfide and diselenide|journal=Inorganic and Nuclear Chemistry Letters|volume=7|page=685|year=1971|doi=10.1016/0020-1650(71)80055-7|issue=7|last2=Jove|first2=J}}</ref> [[selenide]]s AmSe<sub>2</sub> and Am<sub>3</sub>Se<sub>4</sub>,<ref name = "AM_S_SE "/><ref name="AM_METALLIDE">{{cite journal|last1=Roddy|first1=J|title=Americium metallides: AmAs, AmSb, AmBi, Am3Se4, and AmSe2|journal=Journal of Inorganic and Nuclear Chemistry|volume=36|page=2531|year=1974|doi=10.1016/0022-1902(74)80466-5|issue=11}}</ref> and [[Telluride (chemistry)|tellurides]] Am<sub>2</sub>Te<sub>3</sub> and AmTe<sub>2</sub>.<ref>{{cite journal|last1=Damien|first1=D|title=Americium tritelluride and ditelluride|journal=Inorganic and Nuclear Chemistry Letters|volume=8|page=501|year=1972|doi=10.1016/0020-1650(72)80262-9|issue=5}}</ref> The [[Nitrogen group|pnictides]] of americium (<sup>243</sup>Am) of the AmX type are known for the elements [[phosphorus]], [[arsenic]],<ref>{{cite journal|last1=Charvillat|first1=J|title=Americium monoarsenide|journal=Inorganic and Nuclear Chemistry Letters|volume=9|page=559|year=1973|doi=10.1016/0020-1650(73)80191-6|issue=5|last2=Damien|first2=D.}}</ref> [[antimony]] and [[bismuth]]. They crystallize in the [[Cubic crystal system|rock-salt]] lattice.<ref Name="AM_METALLIDE"/>
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| ===Silicides and borides===
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| Americium [[silicide|monosilicide]] (AmSi) and "disilicide" (nominally AmSi<sub>x</sub> with: 1.87 < x < 2.0) were obtained by reduction of americium(III) fluoride with elementary [[silicon]] in vacuum at 1050 °C (AmSi) and 1150−1200 °C (AmSi<sub>x</sub>). AmSi is a black solid isomorphic with LaSi, it has an orthorhombic crystal symmetry. AmSi<sub>x</sub> has a bright silvery lustre and a tetragonal crystal lattice (space group ''I''4<sub>1</sub>/amd), it is isomorphic with PuSi<sub>2</sub> and ThSi<sub>2</sub>.<ref>{{cite journal|last1=Weigel|first1=F|last2=Wittmann|first2=F|last3=Marquart|first3=R|title=Americium monosilicide and "disilicide"|journal=Journal of the Less Common Metals|volume=56|page=47|year=1977|doi=10.1016/0022-5088(77)90217-X}}</ref> [[Boride]]s of americium include AmB<sub>4</sub> and AmB<sub>6</sub>. The tetraboride can be obtained by heating an oxide or halide of americium with [[magnesium diboride]] in vacuum or inert atmosphere.<ref>Lupinetti, A. J. ''et al.'' {{US patent|6830738}} "Low-temperature synthesis of actinide tetraborides by solid-state metathesis reactions", Filed 4 Apr 2002, Issued 14 Dec 2004</ref><ref>{{cite journal|last1=Eick|first1=Harry A.|last2=Mulford|first2=R.N.R.|title=Americium and neptunium borides|journal=Journal of Inorganic and Nuclear Chemistry|volume=31|page=371|year=1969|doi=10.1016/0022-1902(69)80480-X|issue=2}}</ref>
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| ===Organoamericium compounds===
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| [[File:Uranocene-3D-balls.png|thumb|120px|(η<sup>8</sup>-C<sub>8</sub>H<sub>8</sub>)<sub>2</sub>Am structure]]
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| Analogous to [[uranocene]], americium forms an organometallic compound with two [[cyclooctatetraene]] ligands, that is (η<sup>8</sup>-C<sub>8</sub>H<sub>8</sub>)<sub>2</sub>Am.<ref>{{cite book| last = Elschenbroich| first = Christoph| title = Organometallchemie| year = 2008| publisher = Vieweg+teubner Verlag| isbn = 978-3-8351-0167-8| page = 589 }}</ref> It also makes trigonal (η<sup>5</sup>-C<sub>5</sub>H<sub>5</sub>)<sub>3</sub>Am complexes with three [[Cyclopentadienyl complex|cyclopentadienyl]] rings.<ref>{{cite book| author = Thomas E. Albrecht-Schmitt| title = Organometallic and Coordination Chemistry of the Actinides| url = http://books.google.com/?id=rgmnVSzFzXMC&pg=PA8| year = 2008| publisher = Springer| isbn = 978-3-540-77836-3| page = 8 }}</ref>
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| Formation of the complexes of the type Am(n-C<sub>3</sub>H<sub>7</sub>-BTP)<sub>3</sub>, where BTP stands for 2,6-di(1,2,4-triazin-3-yl)pyridine, in solutions containing n-C<sub>3</sub>H<sub>7</sub>-BTP and Am<sup>3+</sup> ions has been confirmed by [[Extended X-ray absorption fine structure|EXAFS]]. Some of these BTP-type complexes selectively interact with americium and therefore are useful in its selective separation from lanthanides and another actinides.<ref>{{cite journal|last1=Girnt|first1=Denise|last2=Roesky|first2=Peter W.|last3=Geist|first3=Andreas|last4=Ruff|first4=Christian M.|last5=Panak|first5=Petra J.|last6=Denecke|first6=Melissa A.|title=6-(3,5-Dimethyl-1H-pyrazol-1-yl)-2,2′-bipyridine as Ligand for Actinide(III)/Lanthanide(III) Separation|journal=Inorganic Chemistry|volume=49|issue=20|pages=9627–35|year=2010|pmid=20849125|doi=10.1021/ic101309j}}</ref>
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| ==Biological aspects==
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| Americium is an artificial element, and thus a biological function involving the element would be impossible.<ref>Toeniskoetter, Steve; Dommer, Jennifer and Dodge, Tony [http://umbbd.msi.umn.edu/periodic/elements/am.html The Biochemical Periodic Tables – Americium], University of Minnesota, Retrieved 28 November 2010</ref><ref>{{cite journal|url=http://www.osti.gov/bridge/product.biblio.jsp?osti_id=2439|author=Dodge, C.J. ''et al.''|title=Role of Microbes as Biocolloids in the Transport of Actinides from a Deep Underground Radioactive Waste Repository|journal=Radiochim. Acta |year=1998|volume=82|pages=347–354}}</ref> It has been proposed to use bacteria for removal of americium and other heavy metals from rivers and streams. Thus, [[Enterobacteriaceae]] of the genus ''[[Citrobacter]]'' precipitate americium ions from aqueous solutions, binding them into a metal-phosphate complex at their cell walls.<ref>{{cite journal|doi=10.1111/j.1574-6976.1994.tb00109.x|last1=MacAskie|first1=LE|last2=Jeong|first2=BC|last3=Tolley|first3=MR|title=Enzymically accelerated biomineralization of heavy metals: application to the removal of americium and plutonium from aqueous flows|journal=FEMS Microbiology Reviews|volume=14|issue=4|pages=351–67|year=1994|pmid=7917422}}</ref> Several studies have been reported on the [[biosorption]] and [[bioaccumulation]] of americium by bacteria<ref>{{cite journal|doi=10.1097/00004032-198601000-00007|last1=Wurtz|first1=EA|last2=Sibley|first2=TH|last3=Schell|first3=WR|title=Interactions of Escherichia coli and marine bacteria with 241Am in laboratory cultures|journal=Health physics|volume=50|issue=1|pages=79–88|year=1986|pmid=3511007}}</ref><ref>{{cite journal|author=Francis, A.J. ''et al.''|title=Role of Bacteria as Biocolloids in the Transport of Actinides from a Deep Underground Radioactive Waste Repository|journal=Acta Radiochimica |year=1998|volume=82|pages= 347–354|osti=2439}}</ref> and fungi.<ref>{{cite journal|last1=Liu|first1=N|last2=Yang|first2=Y|last3=Luo|first3=S|last4=Zhang|first4=T|last5=Jin|first5=J|last6=Liao|first6=J|last7=Hua|first7=X|title=Biosorption of 241Am by Rhizopus arrihizus: preliminary investigation and evaluation|journal=Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine|volume=57|issue=2|pages=139–43|year=2002|pmid=12150270}}</ref>
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| ==Fission==
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| The isotope <sup>242m1</sup>Am (half-life 141 years) has the largest cross sections for absorption of thermal neutrons (5,700 [[Barn (unit)|barns]]),<ref name = "Karlsruhe">Pfennig, G.; Klewe-Nebenius, H and Seelmann Eggebert, W. (Eds.): Karlsruhe [[nuclide]], 7 Edition 2006.</ref> that results in a small [[critical mass]] for a sustained [[nuclear chain reaction]]. The critical mass for a bare <sup>242m1</sup>Am sphere is about 9–14 kg (the uncertainty results from insufficient knowledge of its material properties). It can be lowered to 3–5 kg with a metal reflector and should become even smaller with a water reflector.<ref>{{cite journal|author=Dias, H.; Tancock, N. and Clayton, A.|title=Critical Mass Calculations for <sup>241</sup>Am, <sup>242m</sup>Am and <sup>243</sup>Am|journal=Nippon Genshiryoku Kenkyujo JAERI|year=2003|pages=618–623|url=http://typhoon.jaea.go.jp/icnc2003/Proceeding/paper/6.5_022.pdf}} [http://sciencelinks.jp/j-east/article/200403/000020040303A0828431.php Abstract]</ref> Such small critical mass is favorable for portable [[nuclear weapon]]s, but those based on <sup>242m1</sup>Am are not known yet, probably because of its scarcity and high price. The critical masses of two other readily available isotopes, <sup>241</sup>Am and <sup>243</sup>Am, are relatively high – 57.6 to 75.6 kg for <sup>241</sup>Am and 209 kg for <sup>243</sup>Am.<ref name="irsn">Institut de Radioprotection et de Sûreté Nucléaire, [http://ec.europa.eu/energy/nuclear/transport/doc/irsn_sect03_146.pdf "Evaluation of nuclear criticality safety data and limits for actinides in transport"], p. 16.</ref> Scarcity and high price yet hinder application of americium as a [[nuclear fuel]] in [[nuclear reactor]]s.<ref>{{cite journal|author= Ronen, Y.; Aboudy, M. and Regev, D.|title=A novel method for energy production using <sup>242m</sup>Am as a nuclear fuel|journal=Nuclear technology |year=2000|volume=129|issue=3|pages=407–417|url=http://cat.inist.fr/?aModele=afficheN&cpsidt=1337515}}</ref>
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| There are proposals of very compact 10-kW high-flux reactors using as little as 20 grams of <sup>242m1</sup>Am. Such low-power reactors would be relatively safe to use as [[neutron source]]s for [[Nuclear medicine|radiation therapy]] in hospitals.<ref>{{cite journal|author=Ronen, Y.; Aboudy, M. and Regev, D.|title=Homogeneous <sup>242m</sup>Am-Fueled Reactor for Neutron Capture Therapy|journal=Nuclear Science and Engineering|year=2001|volume=138|issue=3|pages=295–304|osti=20804726}}</ref>
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| ==Isotopes==
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| {{See also|Isotopes of americium}}
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| About 19 [[isotope]]s and 8 [[nuclear isomer]]s are known for americium. There are two long-lived alpha-emitters, <sup>241</sup>Am and <sup>243</sup>Am with half-lives of 432.2 and 7,370 years, respectively, and the nuclear isomer <sup>242m1</sup>Am has a long half-life of 141 years. The half-lives of other isotopes and isomers range from 0.64 microseconds for <sup>245m1</sup>Am to 50.8 hours for <sup>240</sup>Am. As with most other actinides, the isotopes of americium with odd number of neutrons have relatively high rate of nuclear fission and low critical mass.<ref name = "nubase"/>
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| [[Americium-241]] decays to <sup>237</sup>Np emitting alpha particles of 5 different energies, mostly at 5.486 MeV (85.2%) and 5.443 MeV (12.8%). Because many of the resulting states are metastable, they also emit [[gamma ray]]s with the discrete energies between 26.3 and 158.5 keV.<ref>{{cite web|url=http://87.139.25.178:81/eng/theory.htm|title=α-decay of <sup>241</sup>Am. Theory – A lecture course on radioactivity|author=Christian Klinck|publisher=University of Technology Kaiserslautern|accessdate=28 November 2010}}</ref>
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| [[Americium-242]] is a short-lived isotope with a half-life of 16.02 h.<ref name="nubase"/> It mostly (82.7%) converts by β-decay to <sup>242</sup>Cm, but also by [[electron capture]] to <sup>242</sup>Pu (17.3%). Both <sup>242</sup>Cm and <sup>242</sup>Pu transform via nearly the same decay chain through <sup>238</sup>Pu down to <sup>234</sup>U.
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| Nearly all (99.541%) of <sup>242m1</sup>Am decays by [[internal conversion]] to <sup>242</sup>Am and the remaining 0.459% by α-decay to <sup>238</sup>Np. The latter breaks down to <sup>238</sup>Pu and then to <sup>234</sup>U.<ref name="nubase"/>
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| [[Americium-243]] transforms by α-emission into <sup>239</sup>Np, which converts by β-decay to <sup>239</sup>Pu, and the <sup>239</sup>Pu changes into <sup>235</sup>U by emitting an α-particle.
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| ==Applications==
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| {{Multiple image|direction=vertical|align=right|image1=Residential smoke detector.jpg|image2=InsideSmokeDetector.jpg|width=200|caption2=Outside and inside view of an americium-based smoke detector}}
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| ===Ionization detectors===
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| {{Main|Americium smoke detector}}
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| Americium is the only synthetic element to have found its way into the household, where one common type of [[smoke detector]] uses <sup>241</sup>Am in the form of americium dioxide as its source of [[ionizing radiation]].<ref>[http://web.archive.org/web/19960101-re_/http://www.uic.com.au/nip35.htm Smoke Detectors and Americium], Nuclear Issues Briefing Paper 35, May 2002. (Internet Archive), Retrieved 28 November 2010</ref> This isotope is preferred over <sup>226</sup>[[radium|Ra]] because it emits 5 times more alpha particles and relatively little harmful γ-radiation. The amount of americium in a typical new smoke detector is 1 [[Curie|microcurie]] (37 [[becquerel|kBq]]) or 0.28 [[microgram]]. This amount declines slowly as the americium decays into [[neptunium]]-237, a different transuranic element with a much longer half-life (about 2.14 million years). With its half-life of 432.2 years, the americium in a smoke detector includes about 3% [[neptunium]] after 19 years, and about 5% after 32 years. The radiation passes through an [[ionization chamber]], an air-filled space between two [[electrode]]s, and permits a small, constant [[Electric current|current]] between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and affects this current, triggering the alarm. Compared to the alternative optical smoke detector, the ionization smoke detector is cheaper and can detect particles which are too small to produce significant light scattering; however, it is more prone to [[Type I and type II errors|false alarms]].<ref>Residential Smoke Alarm Performance, Thomas Cleary. Building and Fire Research Laboratory, National Institute of Standards and Technology; UL Smoke and Fire Dynamics Seminar. November 2007</ref><ref name="NIST">Bukowski, R. W. ''et al.'' (2007) [http://www.fire.nist.gov/bfrlpubs/fire07/art063.html Performance of Home Smoke Alarms Analysis of the Response of Several Available Technologies in Residential Fire Settings], NIST Technical Note 1455-1</ref><ref>{{cite web |url=http://media.cns-snc.ca/pdf_doc/ecc/smoke_am241.pdf|title = Smoke detectors and americium-241 fact sheet|publisher = Canadian Nuclear Society|accessdate =31 August 2009}}</ref><ref>{{cite web|url=http://www.atsdr.cdc.gov/toxprofiles/tp156.pdf|format=PDF; 2.1MiB|title=Toxicological Profile For Americium|author=Julie Louise Gerberding|publisher=[[United States Department of Health and Human Services]]/[[Agency for Toxic Substances and Disease Registry]]|accessdate=29 August 2009|date=2004| archiveurl= http://web.archive.org/web/20090906112953/http://www.atsdr.cdc.gov/toxprofiles/tp156.pdf| archivedate= 6 September 2009 | deadurl= no}}</ref>
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| ===Radionuclide===
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| As <sup>241</sup>Am has a significantly longer half-life than <sup>238</sup>Pu (432.2 years vs. 87 years), it has been proposed as an active element of [[radioisotope thermoelectric generator]]s, for example in spacecraft.<ref name="RTG">[http://fti.neep.wisc.edu/neep602/SPRING00/lecture5.pdf Basic elements of static RTGs], G.L. Kulcinski, NEEP 602 Course Notes (Spring 2000), Nuclear Power in Space, University of Wisconsin Fusion Technology Institute (see last page)</ref> Although americium produces less heat and electricity – the power yield is 114.7 mW/g for <sup>241</sup>Am and 6.31 mW/g for <sup>243</sup>Am<ref name=res/> (cf. 390 mW/g for <sup>238</sup>Pu)<ref name="RTG"/> – and its radiation poses more threat to humans owing to neutron emission, the [[European Space Agency]] is planning to use americium for its space probes.<ref>[http://www.spaceflightnow.com/news/n1007/09rtg/ Space agencies tackle waning plutonium stockpiles], Spaceflight now, 9 July 2010</ref>
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| Another proposed space-related application of americium is a fuel for space ships with nuclear propulsion. It relies on the very high rate of nuclear fission of <sup>242m</sup>Am, which can be maintained even in a micrometer-thick foil. Small thickness avoids the problem of self-absorption of emitted radiation. This problem is pertinent to uranium or plutonium rods, in which only surface layers provide alpha-particles.<ref name="rocket">{{cite news|title = Extremely Efficient Nuclear Fuel Could Take Man To Mars In Just Two Weeks|publisher = [[ScienceDaily]]|date = 3 January 2001|url = http://www.sciencedaily.com/releases/2001/01/010103073253.htm|accessdate =22 November 2007| archiveurl= http://web.archive.org/web/20071017120211/http://www.sciencedaily.com/releases/2001/01/010103073253.htm| archivedate= 17 October 2007 | deadurl= no}}</ref><ref>{{cite conference|title = An americium-fueled gas core nuclear rocket|booktitle = AIP Conf. Proc.|date = 10 January 1993|volume = 271|pages = 585–589|conference = Tenth symposium on space nuclear power and propulsion|author = Kammash, T. ''et al.''|doi = 10.1063/1.43073}}</ref> The fission products of <sup>242m</sup>Am can either directly propel the spaceship or they can heat up a thrusting gas; they can also transfer their energy to a fluid and generate electricity through a [[MHD generator|magnetohydrodynamic generator]].<ref name="mprice">{{cite journal|last1=Ronen|first1=Y|last2=Shwageraus|first2=E|title=Ultra-thin 242mAm fuel elements in nuclear reactors|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|volume=455|page=442|year=2000|doi=10.1016/S0168-9002(00)00506-4|issue=2|bibcode = 2000NIMPA.455..442R }}</ref>
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| One more proposal which utilizes the high nuclear fission rate of <sup>242m</sup>Am is a nuclear battery. Its design relies not on the energy of the emitted by americium alpha particles, but on their charge, that is the americium acts as the self-sustaining "cathode". A single 3.2 kg <sup>242m</sup>Am charge of such battery could provide about 140 kW of power over a period of 80 days.<ref>Genuth, Iddo [http://thefutureofthings.com/articles.php?itemId=26/64/ Americium Power Source], The Future of Things, 3 October 2006, Retrieved 28 November 2010</ref> With all the potential benefits, the current applications of <sup>242m</sup>Am are as yet hindered by the scarcity and high price of this [[nuclear isomer]].<ref name=mprice/>
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| ===Neutron source===
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| The oxide of <sup>241</sup>Am pressed with [[beryllium]] is an efficient [[neutron source]]. Here americium acts as the alpha source, and beryllium produces neutrons owing to its large cross-section for the (α,n) nuclear reaction:
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| : <math>\mathrm{^{241\!\,}_{\ 95}Am\ \longrightarrow \ ^{237}_{\ 93}Np\ +\ ^{4}_{2}He\ +\ \gamma}</math>
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| : <math>\mathrm{^{9}_{4}Be\ +\ ^{4}_{2}He\ \longrightarrow \ ^{12}_{\ 6}C\ +\ ^{1}_{0}n\ +\ \gamma}</math>
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| The most widespread use of <sup>241</sup>AmBe neutron sources is a [[neutron probe]] – a device used to measure the quantity of water present in soil, as well as moisture/density for quality control in highway construction. <sup>241</sup>Am neutron sources are also used in well logging applications, as well as in [[neutron radiography]], tomography and other radiochemical investigations.<ref name="Binder"/>
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| ===Production of other elements===
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| Americium is a starting material for the production of other transuranic elements and [[transactinide]]s – for example, 82.7% of <sup>242</sup>Am decays to <sup>242</sup>Cm and 17.3% to <sup>242</sup>Pu. In the nuclear reactor, <sup>242</sup>Am is also up-converted by neutron capture to <sup>243</sup>Am and <sup>244</sup>Am, which transforms by β-decay to <sup>244</sup>Cm:
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| : <math>\mathrm{^{243}_{\ 95}Am\ \xrightarrow {(n,\gamma)} \ ^{244}_{\ 95}Am\ \xrightarrow [10.1 \ h]{\beta^-} \ ^{244}_{\ 96}Cm}</math>
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| Irradiation of <sup>241</sup>Am by <sup>12</sup>C or <sup>22</sup>Ne ions yields the isotopes <sup>247</sup>Es ([[einsteinium]]) or <sup>260</sup>Db ([[dubnium]]), respectively.<ref name="Binder">{{cite book| author = Harry H. Binder| title = Lexikon der chemischen Elemente: das Periodensystem in Fakten, Zahlen und Daten : mit 96 Abbildungen und vielen tabellarischen Zusammenstellungen| year = 1999| isbn = 978-3-7776-0736-8 }}</ref> Furthermore, the element [[berkelium]] (<sup>243</sup>Bk isotope) had been first intentionally produced and identified by bombarding <sup>241</sup>Am with alpha particles, in 1949, by the same Berkeley group, using the same 60-inch cyclotron. Similarly, [[nobelium]] was produced at the [[Joint Institute for Nuclear Research]], [[Dubna]], Russia, in 1965 in several reactions, one of which included irradiation of <sup>243</sup>Am with <sup>15</sup>N ions. Besides, one of the synthesis reactions for [[lawrencium]], discovered by scientists at Berkeley and Dubna, included bombardment of <sup>243</sup>Am with <sup>18</sup>O.<ref name=g1252/>
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| ===Spectrometer===
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| Americium-241 has been used as a portable source of both gamma rays and alpha particles for a number of medical and industrial uses. The 60-keV gamma ray emissions from <sup>241</sup>Am in such sources can be used for indirect analysis of materials in [[radiography]] and [[X-ray fluorescence]] spectroscopy, as well as for quality control in fixed [[nuclear density gauge]]s and [[nuclear densometer]]s. For example, the element has been employed to gauge [[glass]] thickness to help create flat glass.<ref name=g1262/> Americium-241 is also suitable for calibration of gamma-ray spectrometers in the low-energy range, since its spectrum consists of nearly a single peak and negligible Compton continuum (at least three orders of magnitude lower intensity).<ref>[http://www.nndc.bnl.gov/nudat2/indx_dec.jsp Nuclear Data Viewer 2.4], NNDC</ref> Americium-241 gamma rays were also used to provide passive diagnosis of thyroid function. This medical application is however obsolete.
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| ==Health concerns==
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| As a highly radioactive element, americium and its compounds must be handled only in an appropriate laboratory under special arrangements. Although most americium isotopes predominantly emit alpha particles which can be blocked by thin layers of common materials, many of the daughter products emit gamma-rays and neutrons which have a long penetration depth.<ref>[http://www.atsdr.cdc.gov/phs/phs.asp?id=809&tid=158 Public Health Statement for Americium] Section 1.5., Agency for Toxic Substances and Disease Registry, April 2004, Retrieved 28 November 2010</ref>
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| If consumed, americium is excreted within a few days and only 0.05% is absorbed in the blood. From there, roughly 45% of it goes to the [[liver]] and 45% to the bones, and the remaining 10% is excreted. The uptake to the liver depends on the individual and increases with age. In the bones, americium is first deposited over [[Cortex (anatomy)|cortical]] and [[trabecula]]r surfaces and slowly redistributes over the bone with time. The biological half-life of <sup>241</sup>Am is 50 years in the bones and 20 years in the liver, whereas in the [[gonad]]s (testicles and ovaries) it remains permanently; in all these organs, americium promotes formation of cancer cells as a result of its radioactivity.<ref name=am/><ref>{{cite web|url=http://www.doh.wa.gov/ehp/rp/factsheets/factsheets-pdf/fs23am241.pdf|author=Division of Environmental Health, Office of Radiation Protection|title=Fact Sheet # 23. Americium-241|date=November 2002|format=PDF|accessdate=28 November 2010| archiveurl= http://web.archive.org/web/20101111125906/http://www.doh.wa.gov/ehp/rp/factsheets/factsheets-pdf/fs23am241.pdf| archivedate= 11 November 2010 | deadurl= no}}</ref><ref>Frisch, Franz ''Crystal Clear, 100 x energy'', Bibliographisches Institut AG, Mannheim 1977, ISBN 3-411-01704-X, p. 184</ref>
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| Americium often enters landfills from discarded [[smoke detector]]s. The rules associated with the disposal of smoke detectors are relaxed in most jurisdictions. In the U.S., the "Radioactive Boy Scout" [[David Hahn]] was able to concentrate americium from smoke detectors after managing to buy a hundred of them at remainder prices and also stealing a few.<ref name="Silverstein2005">[[Ken Silverstein]], [http://www.harpers.org/archive/1998/11/0059750 The Radioactive Boy Scout: When a teenager attempts to build a breeder reactor]. ''[[Harper's Magazine]]'', November 1998</ref><ref>{{cite news|publisher = [[Fox News]] |url= http://www.foxnews.com/story/0,2933,292111,00.html |title='Radioactive Boy Scout' Charged in Smoke Detector Theft|date=4 August 2007|accessdate=28 November 2007| archiveurl= http://web.archive.org/web/20071208062559/http://www.foxnews.com/story/0,2933,292111,00.html| archivedate= 8 December 2007 | deadurl= no}}</ref><ref>{{cite news|work=Detroit Free Press|url= http://www.freep.com/apps/pbcs.dll/article?AID=/20070827/BUSINESS05/70827091 |title=Man dubbed 'Radioactive Boy Scout' pleads guilty |date=27 August 2007 |agency=Associated Press |accessdate=27 August 2007 |archiveurl = http://web.archive.org/web/20070929095926/http://www.freep.com/apps/pbcs.dll/article?AID=/20070827/BUSINESS05/70827091|archivedate = 29 September 2007}}</ref><ref>{{cite news|publisher = [[Fox News]]|url= http://www.foxnews.com/story/0,2933,299362,00.html |title= 'Radioactive Boy Scout' Sentenced to 90 Days for Stealing Smoke Detectors|date=4 October 2007|accessdate=28 November 2007| archiveurl= http://web.archive.org/web/20071113123408/http://www.foxnews.com/story/0,2933,299362,00.html| archivedate= 13 November 2007 | deadurl= no}}</ref> There have been cases of humans being contaminated with americium, the worst case being that of [[Harold McCluskey]], who at the age of 64 was exposed to 500 times the occupational standard for americium-241 as a result of an explosion in his lab. McCluskey died at the age of 75, not as a result of exposure, but of a [[heart disease]] which he had before the accident.<ref name="tristateherald">{{cite news|first = Annette|last = Cary|title=Doctor remembers Hanford's 'Atomic Man'|publisher = ''Tri-City Herald''|url = http://www.hanfordnews.com/news/2008/story/11403.html|date=25 April 2008|accessdate=17 June 2008}}</ref><ref>{{cite news|author = AP wire|title = Hanford nuclear workers enter site of worst contamination accident|url = http://www.billingsgazette.com/index.php?id=1&display=rednews/2005/06/03/build/nation/94-contamination.inc|date = 3 June 2005|accessdate =17 June 2007 |archiveurl=http://health.phys.iit.edu/extended_archive/2005-June/002075.html |archivedate=13 June 2005}}</ref>
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| ==See also==
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| {{Wikipedia books|Americium}}
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| * [[Actinides in the environment]]
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| * [[:Category:Americium compounds]]
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| ==Notes==
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| {{Reflist|group=note}}
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| ==References==
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| {{Reflist|30em}}
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| ==Bibliography==
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| * {{Greenwood&Earnshaw2nd}}
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| * {{cite book| last = Wiberg| first = Nils| title = Lehrbuch Der Anorganischen Chemie| year = 2007| publisher = De Gruyter| isbn = 978-3-11-017770-1 }}
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| * Penneman, R. A. and Keenan T. K. [http://www.osti.gov/bridge/purl.cover.jsp?purl=/4187189-IKQUwY/ The radiochemistry of americium and curium], University of California, Los Alamos, California, 1960
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| ==Further reading==
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| * ''Nuclides and Isotopes – 14th Edition'', GE Nuclear Energy, 1989.
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| * {{cite web|url = http://www.cea.fr/var/cea/storage/static/gb/library/Clefs46/pagesg/clefs46_30.html|title = Can the minor actinide, americium-241, be transmuted by thermal neutrons?|author = Fioni, Gabriele; Cribier, Michel and Marie, Frédéric |publisher = [[Commissariat à l'énergie atomique]]}}
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| * {{cite book| last = Stwertka| first = Albert| title = A Guide to the Elements| year = 1999| publisher = Oxford University Press, USA| isbn = 0-19-508083-1 }}
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| ==External links==
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| {{Commons|Americium}}
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| {{Wiktionary|americium}}
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| * [http://www.periodicvideos.com/videos/095.htm Americium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
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| * [http://www.atsdr.cdc.gov/toxprofiles/phs156.html ATSDR – Public Health Statement: Americium]
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| * [http://world-nuclear.org/info/inf57.html World Nuclear Association – Smoke Detectors and Americium ]
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| {{Clear}}
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| {{Compact periodic table}}
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| {{Americium compounds}}
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| {{Chemical elements named after places}}
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| [[Category:Actinides]]
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| [[Category:Americium]]
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| [[Category:Carcinogens]]
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| [[Category:Chemical elements]]
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| [[Category:Synthetic elements]]
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| {{link FA|de}}
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