View source for Americium

{{Elementbox_header | number=95 | symbol=Am | name=americium | left=[[plutonium]] | right=[[curium]] | above=[[europium|Eu]] | below=(Uqp) | color1=#ff99cc | color2=black }}
{{Elementbox_series | [[actinide]]s }}
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{{Elementbox_atomicmass_gpm | [[1 E-25 kg|(243)]] }}
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{{Elementbox_boilingpoint | k=2880 | c=2607 | f=4725 }}
{{Elementbox_heatfusion_kjpmol | 14.39 }}
{{Elementbox_heatcapacity_jpmolkat25 | 62.7 }}
{{Elementbox_vaporpressure_katpa | 1239 | 1356 | &nbsp; | &nbsp; | &nbsp; | &nbsp; | comment= }}
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{{Elementbox_oxistates | 6, 5, 4, '''3'''<br />([[amphoteric]] oxide) }}
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{{Elementbox_ionizationenergies1 | 578 }}
{{Elementbox_atomicradius_pm | [[1 E-10 m|175]] }}
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 | na=[[synthetic radioisotope|syn]] | hl=[[1 E10 s|432.2 y]]
 | dm1=[[spontaneous fission|SF]] | de1=- | pn1= | ps1=-
 | dm2=[[alpha decay|α]] | de2=5.638 | pn2=237 | ps2=[[neptunium|Np]] }}
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 | dm2=α | de2=5.438 | pn2=239 | ps2=[[neptunium|Np]] }}
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{{SI}}


==Overview==
'''Americium''' ([[International Phonetic Alphabet|IPA]]: {{IPA|/ˌaməˈrɪsiəm/}}) is a [[synthetic element]] that has the symbol '''Am''' and [[atomic number]] 95. A [[radioactive decay|radioactive]] [[metal]]lic element, americium is an [[actinide]] that was obtained by bombarding [[plutonium]] with [[neutron]]s and was the fourth [[transuranic element]] to be discovered. It was named for the [[Americas]], by analogy with [[europium]].

== Notable characteristics ==
Pure americium has a silvery and white [[Lustre (mineralogy)|lustre]]. At [[room temperature]]s it slowly tarnishes in dry air. It is more silvery than [[plutonium]] or [[neptunium]] and apparently more malleable than neptunium or [[uranium]]. [[Alpha emission]] from <sup>241</sup>Am is approximately three times that of [[radium]].  [[Gram]] quantities of <sup>241</sup>Am emit intense [[gamma ray]]s which creates a serious exposure problem for anyone handling the element.

Americium is also [[fissile]]; the critical mass for an unreflected sphere of <sup>241</sup>Am is approximately 60 kilograms.  It is unlikely that Americium would be used as a weapons material, as its minimum critical mass is considerably larger than more readily obtained [[plutonium]] or [[uranium]] isotopes. [http://www.fissilematerials.org/ipfm/pages_us_en/fissile/fissile/fissile.php]

''Please see [[Actinides in the environment]] for more details of the environmental aspects of this element.''

== Applications ==
This element can be produced in [[kilogram]] amounts and has some uses (mostly <sup>241</sup>Am since it is easier to produce relatively pure samples of this isotope). Americium has found its way into the household, where one type of [[smoke detector]] contains a tiny amount (about 0.2 [[microgram]]) of <sup>241</sup>Am as a source of [[ionizing radiation]]. <sup>241</sup>Am has been used as a portable gamma ray source for use in [[radiography]]. The element has also been employed to gauge [[glass]] thickness to help create flat glass.  <sup>242</sup>Am is a neutron emitter and has found uses in [[neutron radiography]]. It has also been cited for use as an advanced nuclear rocket propulsion fuel[http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APCPCS000271000001000585000001&idtype=cvips&gifs=yes]. This isotope is, however, extremely expensive to produce in usable quantities.

<!-- From Americium nuclear fuel article, merging

The isotope <sup>242m</sup>Am with a half life of 141 years has superior nuclear properties which are related to fission, compared to any known nuclear fuel.
This isotope was suggested as a nuclear fuel in 1988 by professor Yigal Ronen from Ben-Gurion University Israel. It was also suggested by Dr. G. Chapline to use this isotope for Fission Fragment Rocket. This isotope was also suggested to use in nuclear batteries for space applications, and other applications.
-->

== History ==
Americium was [[discovery of the chemical elements|first isolated]] by [[Glenn T. Seaborg]], Leon O. Morgan, Ralph A. James, and [[Albert Ghiorso]] in late [[1944]] at the wartime Metallurgical Laboratory at the [[University of Chicago]] (now known as [[Argonne National Laboratory]]). The team created the [[isotope]] <sup>241</sup>Am by subjecting <sup>239</sup>[[plutonium|Pu]] to successive [[neutron capture]] reactions in a [[nuclear reactor]]. This created <sup>240</sup>Pu and then <sup>241</sup>Pu which in turn decayed into <sup>241</sup>Am via [[beta decay]].  Seaborg was granted {{US patent|3156523}} for "Element 95 and Method of Producing Said Element," whose unusually terse claim number 1 reads simply, "Element 95."  The discovery of americium and [[curium]] was first announced informally on a children's quiz show in 1945. [http://pubs.acs.org/cen/80th/print/americiumprint.html]

== Isotopes ==<!-- This section is linked from [[Alpha decay]] -->
{{main|isotopes of americium}}
[[Image:Americium.jpg|left|150px|thumb|Sample of Americium]]18 [[radioisotope]]s of americium have been characterized, with the most stable being <sup>243</sup>Am with a [[half-life]] of 7370 years, and <sup>241</sup>Am with a half-life of 432.7 years. All of the remaining [[radioactive decay|radioactive]] isotopes have half-lives that are less than 51 hours, and the majority of these have half-lives that are less than 100 minutes. This element also has 8 [[meta state]]s, with the most stable being <sup>242m</sup>Am (t<sub>½</sub> 141 years). The isotopes of americium range in [[atomic weight]] from 231.046 [[atomic mass unit|u]] (<sup>231</sup>Am) to 249.078 u (<sup>249</sup>Am).

== Chemistry ==

In aqueous systems the most common oxidation state is +3. It is very much harder to oxidize Am(III) to Am(IV) than it is to oxidise Pu(III) to Pu(IV).

Currently the [[solvent extraction]] chemistry of americium is important as in several areas of the world [[scientists]] are working on reducing the medium term [[Ionizing radiation|radiotoxicity]] of the waste from the reprocessing of used [[nuclear fuel]].

See [[liquid-liquid extraction]] for some examples of the solvent extraction of americium.

Americium, unlike uranium, does not readily form a dioxide americyl core (AmO<sub>2</sub>). [http://fas.org/sgp/othergov/doe/lanl/pubs/00818038.pdf] This is because americium is very hard to oxidise above the +3 oxidation state when it is in an aqeuous solution.  In the environment, this americyl core could complex with carbonate as well as other oxygen moieties (OH<sup>-</sup>, NO<sub>2</sub><sup>-</sup>, NO<sub>3</sub><sup>-</sup>, and SO<sub>4</sub><sup>-2</sup>) to form charged complexes which tend to be readily mobile with low affinities to soil.

*AmO<sub>2</sub>(OH)<sup>+1</sup>
*AmO<sub>2</sub>(OH)<sub>2</sub><sup>+2</sup>
*AmO<sub>2</sub>CO<sub>3</sub><sup>+1</sup>
*AmO<sub>2</sub>(CO<sub>3</sub>)<sub>2</sub><sup>-1</sup>
*AmO<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub><sup>-3</sup>

A large amount of work has been done on the [[solvent extraction]] of americium, as it is the case that americium and the other transplutonium elements are responsible for the majority of the long lived radiotoxicity of [[spent nuclear fuel]]. It is thought that by removal of the americium and [[curium]] that the used fuel will only need to be isolated from man and his environment for a shorter time than that required for the isolation of untreated used fuel. One recent [[EU]] funded project on this topic was known by the codename "EUROPART". Within this project [[triazines]] and other compounds were studied as potential extraction agents.

<ref>[http://www.nea.fr/html/pt/docs/iem/madrid00/Proceedings/Paper14.pdf]</ref><ref>[http://www-atalante2004.cea.fr/home/liblocal/docs/atalante2000/P3-26.pdf]</ref><ref>[http://www.nea.fr/html/pt/docs/iem/jeju02/session2/SessionII-15.pdf]</ref><ref>[http://www.rsc.org/delivery/_ArticleLinking/DisplayArticleForFree.cfm?doi=b301178j&JournalCode=DT]</ref><ref>[http://www.tntech.edu/WRC/pdfs/Projects04_05/Ens_Elem.pdf]</ref>

==References==
<references/>
==External links==
*[http://periodic.lanl.gov/elements/95.html Los Alamos National Laboratory - Americium]
*''Guide to the Elements - Revised Edition'', Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
* [http://education.jlab.org/itselemental/ele095.html It's Elemental - Americium]
*[http://www.atsdr.cdc.gov/toxprofiles/phs156.html ATSDR - Public Health Statement: Americium]
*''Nuclides and Isotopes - 14th Edition'', GE Nuclear Energy, 1989.
*Patent {{US patent reference
 | number = 3156523
 | y = 1964
 | m = 11
 | d = 10
 | inventor = Glenn T. Seaborg
 | title = Element 95 and Method of Producing Said Element
}}
*[http://www.cea.fr/var/cea/storage/static/gb/library/Clefs46/pagesg/clefs46_30.html CEA] Can the minor actinide, americium-241, be transmuted by thermal neutrons?
*[http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=APCPCS000271000001000585000001&idtype=cvips&gifs=yes American Institude of Physics Conference Proceedings]
{{Commons|Americium}}
{{wiktionary|americium}}
* [http://www.webelements.com/webelements/elements/text/Am/index.html WebElements.com - Americium] (also used as a reference)
* [http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@rn+@rel++@OR+@na+americium,+radioactive NLM Hazardous Substances Databank - Americium, radioactive]

[[Category:Actinides]]
[[Category:Americium]]
[[Category:Carcinogens]]

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