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| {{Redirect|Athenium||Athenaeum (disambiguation){{!}}Athenaeum}}
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| {{infobox einsteinium}}
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| '''Einsteinium''' is a [[synthetic element]] with the symbol '''Es''' and [[atomic number]] 99. It is the seventh [[transuranic element]], and an [[actinide]].
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| Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after [[Albert Einstein]]. Its most common [[isotope]] einsteinium-253 (half life 20.47 days) is produced artificially from decay of californium-253 in a few dedicated high-power [[nuclear reactor]]s with a total yield on the order of one milligram per year. The reactor synthesis is followed by a complex procedure of separating einsteinium-253 from other actinides and products of their decay. Other isotopes are synthesized in various laboratories, but at much smaller amounts, by bombarding heavy actinide elements with light ions. Owing to the small amounts of produced einsteinium and the short half-life of its most easily produced isotope, there are currently almost no practical applications for it outside of basic scientific research. In particular, einsteinium was used to synthesize, for the first time, 17 atoms of the new element [[mendelevium]] in 1955.
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| Einsteinium is a soft, silvery, [[paramagnetism|paramagnetic]] [[metal]]. Its chemistry is typical of the late actinides, with a preponderance of the +3 [[oxidation state]]; the +2 oxidation state is also accessible, especially in solids. The high radioactivity of einsteinium-253 produces a visible glow and rapidly damages its crystalline metal lattice, with released heat of about 1000 [[watt]]s per gram. Difficulty in studying its properties is due to einsteinium-253's conversion to [[berkelium]] and then [[californium]] at a rate of about 3% per day. The isotope of einsteinium with the longest half life, einsteinium-252 (half life 471.7 days) would be more suitable for investigation of physical properties, but it has proven far more difficult to produce and is available only in minute quantities, and not in bulk.<ref>[http://periodic.lanl.gov/99.shtml Einsteinium]. periodic.lanl.gov</ref> Einsteinium is the element with the highest atomic number which has been observed in macroscopic quantities in its pure form, and this was the common short-lived isotope einsteinium-253.<ref name=h1579/>
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| Like all synthetic [[transuranic element]]s, isotopes of einsteinium are extremely [[radioactivity|radioactive]] and are considered highly dangerous to health on ingestion.<ref name=CRC/>
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| ==History==
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| [[File:Ivy Mike - mushroom cloud.jpg|thumb|left|Einsteinium was first observed in the fallout from the ''Ivy Mike'' nuclear test.]]
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| [[File:Einstein1921 by F Schmutzer 2.jpg|thumb|left|The element was named after [[Albert Einstein]].]] | |
| Einsteinium was [[discovery of the chemical elements|first identified]] in December 1952 by [[Albert Ghiorso]] and co-workers at the [[University of California, Berkeley]] in collaboration with the [[Argonne National Laboratory|Argonne]] and [[Los Alamos National Laboratory|Los Alamos]] National Laboratories, in the fallout from the ''[[Ivy Mike]]'' nuclear test. The test was carried out on November 1, 1952 at [[Enewetak Atoll]] in the [[Pacific Ocean]] and was the first successful test of a [[hydrogen bomb]].<ref name="Ghiorso"/> Initial examination of the debris from the explosion had shown the production of a new isotope of [[plutonium]], {{Nuclide|Pu|Z=94|A=244}}, which could only have formed by the absorption of six [[neutron]]s by a [[uranium-238]] nucleus followed by two [[beta decay]]s.
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| :<math>\mathrm{^{238}_{\ 92}U\ \xrightarrow [-2\ \beta^-]{+\ 6\ (n,\gamma)} \ ^{244}_{\ 94}Pu}</math>
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| At the time, the multiple neutron absorption was thought to be an extremely rare process, but the identification of {{Nuclide2|Pu|Z=94|A=244}} indicated that still more neutrons could have been captured by the uranium nuclei, thereby producing new elements heavier than [[californium]].<ref name="Ghiorso">{{cite journal|first = Albert|last = Ghiorso|authorlink = Albert Ghiorso|year = 2003 |title = Einsteinium and Fermium|journal = Chemical and Engineering News|url = http://pubs.acs.org/cen/80th/einsteiniumfermium.html|volume = 81|issue = 36|doi = 10.1021/cen-v081n036.p174|pages = 174}}</ref>
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| Ghiorso and co-workers analyzed filter papers which had been flown through the explosion cloud on airplanes (the same sampling technique that had been used to discover {{Nuclide|Pu|Z=94|A=244}}).<ref name=s39>[[#Seaborg|Seaborg]], p. 39</ref> Larger amounts of radioactive material were later isolated from coral debris of the atoll, which were delivered to the U.S.<ref name="Ghiorso"/> The separation of suspected new elements was carried out in the presence of a [[citric acid]]/[[ammonium]] [[buffer solution]] in a weakly acidic medium ([[pH]] ≈ 3.5), using [[ion exchange]] at elevated temperatures; fewer than 200 atoms of einsteinium were recovered in the end.<ref name=em>John Emsley [http://books.google.com/books?id=j-Xu07p3cKwC&pg=PA133 Nature's building blocks: an A-Z guide to the elements], Oxford University Press, 2003, ISBN 0-19-850340-7 pp. 133–135</ref> Nevertheless, element 99 (einsteinium), namely its <sup>253</sup>Es isotope, could be detected via its characteristic high-energy [[alpha decay]] at 6.6 MeV.<ref name = "Ghiorso"/> It was produced by the [[neutron capture|capture]] of 15 [[neutron]]s by [[uranium-238]] nuclei followed by seven beta-decays, and had a [[half-life]] of 20.5 days. Such multiple neutron absorption was made possible by the high neutron flux density during the detonation, so that newly generated heavy isotopes had plenty of available neutrons to absorb before they could disintegrate into lighter elements. Neutron capture initially raised the [[mass number]] without changing the [[atomic number]] of the nuclide, and the concomitant beta-decays resulted in a gradual increase in the atomic number:<ref name="Ghiorso"/>
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| :<math>\mathrm{^{238}_{\ 92}U\ \xrightarrow [6 \beta^-]{+\ 15 n} \ ^{253}_{\ 98}Cf\ \xrightarrow{\beta^-} \ ^{253}_{\ 99}Es}</math>
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| Some <sup>238</sup>U atoms, however, could absorb another two neutrons (for a total of 17), resulting in <sup>255</sup>Es, as well as in the <sup>255</sup>Fm isotope of another new element, [[fermium]].<ref><sup>254</sup>Es, <sup>254</sup>Fm and <sup>253</sup>Fm would not be produced because of lack of beta decay in <sup>254</sup>Cf and <sup>253</sup>Es</ref> The discovery of the new elements and the associated new data on multiple neutron capture were initially kept secret on the orders of the U.S. military until 1955 due to [[Cold War]] tensions and competition with Soviet Union in nuclear technologies.<ref name="Ghiorso"/><ref name = "ES_FM">{{cite journal|last1 = Ghiorso|first1 = A.|last2 = Thompson|first2 = S.|last3 = Higgins|first3 = G.|last4 = Seaborg|first4 = G.|last5 = Studier|first5 = M.|last6 = Fields|first6 = P.|last7 = Fried|first7 = S.|last8 = Diamond|first8 = H.|last9 = Mech|first9 = J.|first10 = G. |last10 = Pyle
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| |first11 = J. |last11 = Huizenga
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| |first12 = A. |last12 = Hirsch
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| |first13 = W. |last13 = Manning
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| |first14 = C. |last14 = Browne
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| |first15 = H. |last15 = Smith
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| |first16 = R. |last16 = Spence
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| |title = New Elements Einsteinium and Fermium, Atomic Numbers 99 and 100|journal = Phys. Rev.|volume = 99| issue = 3|url=http://escholarship.org/uc/item/70q401ct|doi = 10.1103/PhysRev.99.1048| pages = 1048–1049| year = 1955|bibcode = 1955PhRv...99.1048G }} [http://books.google.com/books?id=e53sNAOXrdMC&pg=PA91 Google Books]</ref><ref>{{cite journal|last1=Fields|first1=P.|last2=Studier|first2=M.|last3=Diamond|first3=H.|last4=Mech|first4=J.|last5=Inghram|first5=M.|last6=Pyle|first6=G.|last7=Stevens|first7=C.|last8=Fried|first8=S.|last9=Manning|first9=W. |first10 = G. |last10 = Pyle |first11 = J. |last11 = Huizenga |first12 = A. |last12 = Hirsch |first13 = W. |last13 = Manning |first14 = C. |last14 = Browne |first15 = H. |last15 = Smith |first16 = R. |last16 = Spence |title=Transplutonium Elements in Thermonuclear Test Debris|journal=Physical Review |volume=102|year=1956|pages=180–182|doi=10.1103/PhysRev.102.180|bibcode = 1956PhRv..102..180F }} [http://books.google.com/books?id=e53sNAOXrdMC&pg=PA93 Google Books]</ref> However, the rapid capture of so many neutrons would provide needed direct experimental confirmation <!--"convincing evidence of the reality of"--> of the so-called [[r-process]] multiple neutron absorption needed to explain the cosmic [[nucleosynthesis]] (production) of certain heavy chemical elements (heavier than nickel) in [[supernova]] explosions, before [[beta decay]]. Such a process is needed to explain the existence of many stable elements in the universe.<ref>Byrne, J. ''Neutrons, Nuclei, and Matter'', Dover Publications, Mineola, NY, 2011, ISBN 978-0-486-48238-5 (pbk.) pp. 267.</ref>
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| Meanwhile, isotopes of element 99 (as well as of new element 100, [[fermium]]) were produced in the Berkeley and Argonne laboratories, in a [[nuclear fusion|nuclear reaction]] between [[nitrogen]]-14 and uranium-238,<ref name = "PhysRev.93.257">{{cite journal| journal = Physical Review| volume = 93|issue = 1| year = 1954|title = Reactions of U-238 with Cyclotron-Produced Nitrogen Ions| author = Ghiorso, Albert; Rossi, G. Bernard; Harvey, Bernard G. and Thompson, Stanley G.| doi = 10.1103/PhysRev.93.257|pages = 257|bibcode = 1954PhRv...93..257G }}</ref> and later by intense neutron irradiation of [[plutonium]] or [[californium]]:
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| :<math>\mathrm{^{252}_{\ 98}Cf\ \xrightarrow {(n,\gamma)} \ ^{253}_{\ 98}Cf\ \xrightarrow [17.81 \ d]{\beta^-} \ ^{253}_{\ 99}Es\ \xrightarrow {(n,\gamma)} \ ^{254}_{\ 99}Es\ \xrightarrow []{\beta^-} \ ^{254}_{100}Fm}</math>
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| These results were published in several articles in 1954 with the disclaimer that these were not the first studies that had been carried out on the elements.<ref name = "PhysRev.93.908" >{{cite journal| journal = Physical Review| volume = 93| year = 1954| title = Transcurium Isotopes Produced in the Neutron Irradiation of Plutonium |author = Thompson, S. G.; Ghiorso, A.; Harvey, B. G.; Choppin, G. R. | doi = 10.1103/PhysRev.93.908| pages = 908| issue = 4
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| |bibcode = 1954PhRv...93..908T }}</ref><ref>{{cite journal|last1=Harvey|first1=Bernard|last2=Thompson|first2=Stanley|last3=Ghiorso|first3=Albert|last4=Choppin|first4=Gregory|title=Further Production of Transcurium Nuclides by Neutron Irradiation|journal=Physical Review|volume=93|pages=1129|year=1954|doi=10.1103/PhysRev.93.1129|issue=5|bibcode = 1954PhRv...93.1129H }}</ref><ref>{{cite journal|last1=Studier|first1=M.|last2=Fields|first2=P.|last3=Diamond|first3=H.|last4=Mech|first4=J.|last5=Friedman|first5=A.|last6=Sellers|first6=P.|last7=Pyle|first7=G.|last8=Stevens|first8=C.|last9=Magnusson|first9=L.|first10=J.|last10=Huizenga |title=Elements 99 and 100 from Pile-Irradiated Plutonium|journal=Physical Review|volume=93|pages=1428|year=1954|doi=10.1103/PhysRev.93.1428|issue=6|bibcode = 1954PhRv...93.1428S }}</ref><ref>{{cite journal|first1 = G. R.|last1 = Choppin|first2 = S. G.|last2 = Thompson|first3 = A.|last3 = Ghiorso|authorlink3 = Albert Ghiorso|first4 = B. G.|last4 = Harvey|title = Nuclear Properties of Some Isotopes of Californium, Elements 99 and 100|journal = Physical Review|volume = 94|issue = 4|pages = 1080–1081|year = 1954|doi = 10.1103/PhysRev.94.1080|bibcode = 1954PhRv...94.1080C }}</ref><ref>{{cite journal|last1=Fields|first1=P.|last2=Studier|first2=M.|last3=Mech|first3=J.|last4=Diamond|first4=H.|last5=Friedman|first5=A.|last6=Magnusson|first6=L.|last7=Huizenga|first7=J.|title=Additional Properties of Isotopes of Elements 99 and 100|journal=Physical Review|volume=94|pages=209|year=1954|doi=10.1103/PhysRev.94.209|bibcode = 1954PhRv...94..209F }}</ref> The Berkeley team also reported some results on the chemical properties of einsteinium and fermium.<ref Name="Properties_1">Seaborg, G. T.; Thompson, S.G.; Harvey, B.G. and Choppin, G.R. (July 23, 1954) [http://www.osti.gov/accomplishments/documents/fullText/ACC0047.pdf "Chemical Properties of Elements 99 and 100"], Radiation Laboratory, University of California, Berkeley, UCRL-2591</ref><ref name="Properties_2">{{cite journal|last1=Thompson|first1=S. G.|last2=Harvey|first2=B. G.|last3=Choppin|first3=G. R.|last4=Seaborg|first4=G. T.|journal=Journal of the American Chemical Society|volume=76|pages=6229|year=1954|doi=10.1021/ja01653a004|issue=24}}</ref> The ''Ivy Mike'' results were declassified and published in 1955.<ref name = "ES_FM"/>
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| In their discovery of the elements 99 and 100, the American teams had competed with a group at the [[Nobel Institute for Physics]], [[Stockholm]], [[Sweden]]. In late 1953 – early 1954, the Swedish group succeeded in the synthesis of light isotopes of element 100, in particular <sup>250</sup>Fm, by bombarding uranium with oxygen nuclei. These results were also published in 1954.<ref>{{cite journal|last1=Atterling|first1=Hugo|last2=Forsling|first2=Wilhelm|last3=Holm|first3=Lennart|last4=Melander|first4=Lars|last5=Åström|first5=Björn|title=Element 100 Produced by Means of Cyclotron-Accelerated Oxygen Ions|journal=Physical Review|volume=95|pages=585|year=1954|doi=10.1103/PhysRev.95.585.2|issue=2|bibcode = 1954PhRv...95..585A }}</ref> Nevertheless, the priority of the Berkeley team was generally recognized, as its publications preceded the Swedish article, and they were based on the previously undisclosed results of the 1952 thermonuclear explosion; thus the Berkeley team was given the privilege to name the new elements. As the effort which had led to the design of ''Ivy Mike'' was codenamed Project PANDA,<ref name="underthecloud">{{cite book |title=Under the cloud: the decades of nuclear testing |author=Richard Lee Miller |page=115 |isbn=1-881043-05-3 |publisher=Two-Sixty Press |year=1991}}</ref> element 99 had been jokingly nicknamed "Pandamonium"<!-- sic: /not/ pandemonium --><ref name="mcphee">{{cite book |title=The Curve of Binding Energy |author=[[John McPhee]] |page=116 |publisher=Farrar, Straus & Giroux Inc; |isbn=0-374-51598-0 |year=1980}}</ref> but the official names suggested by the Berkeley group derived from two prominent and recently deceased scientists, [[Albert Einstein]] (died 18 April 1955) and [[Enrico Fermi]] (died 28 November 1954):<ref>The names were proposed before their deaths, but announced after.</ref> "We suggest for the name for the element with the atomic number 99, einsteinium (symbol E) after Albert Einstein and for the name for the element with atomic number 100, fermium (symbol Fm), after Enrico Fermi."<ref name = "ES_FM "/> The discovery of these new elements was announced by [[Albert Ghiorso]] at the first Geneva Atomic Conference held on 8–20 August 1955.<ref name="Ghiorso"/> The symbol for einsteinium was first given as "E" and later changed to "Es" by IUPAC.<ref name=h1577>[[#Haire|Haire]], p. 1577</ref><ref name=se6>Seaborg, G.T. (1994) ''[http://books.google.com/books?id=e53sNAOXrdMC&pg=PA6 Modern alchemy: selected papers of Glenn T. Seaborg]'', World Scientific, p. 6, ISBN 981-02-1440-5.</ref>
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| ==Characteristics==
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| ===Physical===
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| [[File:EinsteiniumGlow.JPG|thumb|upright|Glow due to the intense radiation from ~300 µg of <sup>253</sup>Es.<ref>[[#Haire|Haire]], p. 1580</ref>]]
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| Einsteinium is a synthetic, silvery-white, radioactive metal. In the [[periodic table]], it is located to the right of the actinide [[californium]], to the left of the actinide [[fermium]] and below the lanthanide [[holmium]] with which it shares many similarities in physical and chemical properties. Its density of 8.84 g/cm<sup>3</sup> is lower than that of californium (15.1 g/cm<sup>3</sup>) and is nearly the same as that of holmium (8.79 g/cm<sup>3</sup>), despite atomic einsteinium being much heavier than holmium. The melting point of einsteinium (860 °C) is also relatively low – below californium (900 °C), fermium (1527 °C) and holmium (1461 °C).<ref name=CRC>Hammond C. R. "The elements" in {{RubberBible86th}}</ref><ref name="HAIRE_1990">Haire, R. G. (1990) "Properties of the Transplutonium Metals (Am-Fm)", in: Metals Handbook, Vol. 2, 10th edition, (ASM International, Materials Park, Ohio), pp. 1198–1201.</ref> Einsteinium is a soft metal, with the [[bulk modulus]] of only 15 GPa, which value is one of the lowest among non-[[alkali metal]]s.<ref name=h1591>[[#Haire|Haire]], p. 1591</ref>
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| Contrary to the lighter actinides californium, berkelium, curium and americium which crystallize in a double [[Hexagonal crystal system|hexagonal]] structure at ambient conditions, einsteinium is believed to have a [[Cubic crystal system|face-centered cubic]] (''fcc'') symmetry with the space group ''Fm{{overline|3}}m'' and the lattice constant ''a'' = 575 pm. However, there is a report of room-temperature hexagonal einsteinium metal with ''a'' = 398 pm and ''c'' = 650 pm, which converted to the ''fcc'' phase upon heating to 300 °C.<ref name=ev/>
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| The self-damage induced by the radioactivity of einsteinium is so strong that it rapidly destroys the crystal lattice,<ref name=g1268/> and the energy release during this process, 1000 watts per gram of <sup>253</sup>Es, induces a visible glow.<ref name=h1579>[[#Haire|Haire]], p. 1579</ref> These processes may contribute to the relatively low density and melting point of einsteinium.<ref Name="ES_METALL">{{cite journal|last1=Haire|first1=R. G.|last2=Baybarz|first2=R. D.|doi=10.1051/jphyscol:1979431|title=Studies of einsteinium metal|year=1979|pages=C4–101|volume=40|journal=Le Journal de Physique |url=http://hal.archives-ouvertes.fr/docs/00/21/88/27/PDF/ajp-jphyscol197940C431.pdf}} [http://www.osti.gov/bridge/servlets/purl/6582609-SrTVod/6582609.pdf draft manuscript]</ref> Further, owing to the small size of the available samples, the melting point of einsteinium was often deduced by observing the sample being heated inside an electron microscope.<ref name=s61>[[#Seaborg|Seaborg]], p. 61</ref> Thus the surface effects in small samples could reduce the melting point value.
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| The metal is divalent and has a noticeably high volatility.<ref>{{cite journal|last1=Kleinschmidt|first1=Phillip D.|last2=Ward|first2=John W.|last3=Matlack|first3=George M.|last4=Haire|first4=Richard G.|title=Henry's Law vaporization studies and thermodynamics of einsteinium-253 metal dissolved in ytterbium|journal=The Journal of Chemical Physics|volume=81|pages=473|year=1984|doi=10.1063/1.447328|bibcode = 1984JChPh..81..473K }}</ref> In order to reduce the self-radiation damage, most measurements of solid einsteinium and its compounds are performed right after thermal annealing.<ref name=s52>[[#Seaborg|Seaborg]], p. 52</ref> Also, some compounds are studied under the atmosphere of the reductant gas, for example H<sub>2</sub>O+[[hydrogen chloride|HCl]] for EsOCl so that the sample is partly regrown during its decomposition.<ref name=s60/>
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| Apart from the self-destruction of solid einsteinium and its compounds, other intrinsic difficulties in studying this element include scarcity – the most common <sup>253</sup>Es isotope is available only once or twice a year in sub-milligram amounts – and self-contamination due to rapid conversion of einsteinium to berkelium and then to californium at a rate of about 3.3% per day:<ref name="ES_F3"/><ref Name="ES2O3"/><ref name=s55>[[#Seaborg|Seaborg]], p. 55</ref>
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| :<math>\mathrm{^{253}_{\ 99}Es\ \xrightarrow [20 \ d]{\alpha} \ ^{249}_{\ 97}Bk\ \xrightarrow [314 \ d]{\beta^-} \ ^{249}_{\ 98}Cf}</math>
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| Thus, most einsteinium samples are contaminated, and their intrinsic properties are often deduced by extrapolating back experimental data accumulated over time. Other experimental techniques to circumvent the contamination problem include selective optical excitation of einsteinium ions by a tunable laser, such as in studying its luminescence properties.<ref name=s76>[[#Seaborg|Seaborg]], p. 76</ref>
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| Magnetic properties have been studied for einsteinium metal, its oxide and fluoride. All three materials showed [[Curie–Weiss law|Curie–Weiss]] [[paramagnetism|paramagnetic]] behavior from [[liquid helium]] to room temperature. The effective magnetic moments were deduced as 10.4 ± 0.3 [[Bohr magneton|µ<sub>B</sub>]] for Es<sub>2</sub>O<sub>3</sub> and 11.4 ± 0.3 µ<sub>B</sub> for the EsF<sub>3</sub>, which are the highest values among actinides, and the corresponding [[Curie temperature]]s are 53 and 37 K.<ref>{{cite journal|last1=Huray|first1=P|last2=Nave|first2=S|last3=Haire|first3=R|title=Magnetism of the heavy 5f elements|journal=Journal of the Less Common Metals|volume=93|pages=293|year=1983|doi=10.1016/0022-5088(83)90175-3|issue=2}}</ref><ref>{{cite journal|last1=Huray|first1=Paul G.|last2=Nave|first2=S.E.|last3=Haire|first3=R.G.|last4=Moore|first4=J.R.|title=Magnetic Properties of Es<sub>2</sub>O<sub>3</sub> and EsF<sub>3</sub>|journal=Inorganica Chimica Acta|volume=94|pages=120|year=1984|doi=10.1016/S0020-1693(00)94587-0}}</ref>
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| ===Chemical===
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| Like all actinides, einsteinium is rather reactive. Its trivalent [[oxidation state]] is most stable in solids and aqueous solution where it induced pale pink color.<ref name="HOWI_1956">[[#Holleman|Holleman]], p. 1956</ref> The existence of divalent einsteinium is firmly established, especially in solid phase; such +2 state is not observed in many other actinides, including [[protactinium]], [[uranium]], [[neptunium]], plutonium, curium and berkelium. Einsteinium(II) compounds can be obtained, for example, by reducing einsteinium(III) with [[samarium(II) chloride]].<ref name=s53>[[#Seaborg|Seaborg]], p. 53</ref> The oxidation state +4 was postulated from vapor studies and is yet uncertain.<ref name=h1578>[[#Haire|Haire]], p. 1578</ref>
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| ===Isotopes===
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| {{main|Isotopes of einsteinium}}
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| Nineteen [[nuclide]]s and three [[nuclear isomer]]s are known for einsteinium with atomic weights ranging from 240 to 258. All are radioactive and the most stable nuclide, <sup>252</sup>Es, has a half-life of 471.7 days.<ref>{{cite journal|last1=Ahmad|first1=I|title=Half-life of the longest-lived einsteinium isotope-252Es|journal=Journal of Inorganic and Nuclear Chemistry|volume=39|pages=1509|year=1977|doi=10.1016/0022-1902(77)80089-4|issue=9|last2=Wagner|first2=Frank}}</ref> Next most stable isotopes are <sup>254</sup>Es (half-life 275.7 days),<ref>{{cite journal|last1=McHarris|first1=William|last2=Stephens|first2=F.|last3=Asaro|first3=F.|last4=Perlman|first4=I.|title=Decay Scheme of Einsteinium-254|journal=Physical Review|volume=144|pages=1031|year=1966|doi=10.1103/PhysRev.144.1031|issue=3|bibcode = 1966PhRv..144.1031M }}</ref> <sup>255</sup>Es (39.8 days) and <sup>253</sup>Es (20.47 days). All of the remaining isotopes have half-lives shorter than 40 hours, and most of them decay within less than 30 minutes. Of the three nuclear isomers, the most stable is <sup>254''m''</sup>Es with half-life of 39.3 hours.<ref name="nubase">{{cite journal|last1=Audi|first1=G|doi=10.1016/S0375-9474(97)00482-X|title=The NUBASE evaluation of nuclear and decay properties|year=1997|pages=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>
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| ===Nuclear fission===
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| Einsteinium has a high rate of [[nuclear fission]] that results in a low [[critical mass]] for a sustained [[nuclear chain reaction]]. This mass is 9.89 kilograms for a bare sphere of <sup>254</sup>Es isotope, and can be lowered to 2.9 or even 2.26 kilograms, respectively, by adding a 30 centimeter thick steel or water reflector. However, even this small critical mass greatly exceeds the total amount of einsteinium isolated thus far, especially of the rare <sup>254</sup>Es isotope.<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>
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| ===Natural occurrence===
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| Because of the short half-life of all isotopes of einsteinium, all [[Primordial nuclide|primordial]] einsteinium, that is einsteinium that could possibly be present on the Earth during its formation, has decayed by now. Synthesis of einsteinium from naturally occurring actinides uranium and thorium in the Earth crust requires multiple neutron capture, which is an extremely unlikely event. Therefore, most einsteinium is produced on Earth in scientific laboratories, high-power nuclear reactors, or in [[nuclear weapons testing|nuclear weapons tests]], and is present only within a few years from the time of the synthesis.<ref name=em/> Einsteinium and [[fermium]] did occur naturally in the [[natural nuclear fission reactor]] at [[Oklo]], but no longer do so.<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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| Einsteinium was observed in a very specular [[Przybylski's Star]] 2008<ref>http://link.springer.com/article/10.3103%2FS0884591308020049</ref>
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| ==Synthesis and extraction==
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| [[File:EsProduction.png|thumb|300px|Early evolution of einsteinium production in the U.S.<ref name=s51>[[#Seaborg|Seaborg]], p. 51</ref>]]
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| Einsteinium is produced in minute quantities by bombarding lighter actinides with neutrons in dedicated high-flux [[nuclear reactor]]s. The world's major irradiation sources are the 85-megawatt High Flux Isotope Reactor (HFIR) at the [[Oak Ridge National Laboratory]] in Tennessee, U.S.,<ref>{{cite web|title = High Flux Isotope Reactor|url = http://neutrons.ornl.gov/facilities/HFIR/|publisher = Oak Ridge National Laboratory|accessdate = 2010-09-23}}</ref> and the SM-2 loop reactor at the [[Research Institute of Atomic Reactors]] (NIIAR) in [[Dimitrovgrad, Russia]],<ref>{{cite web|title = Радионуклидные источники и препараты|url = http://www.niiar.ru/?q=radioisotope_application|publisher = Research Institute of Atomic Reactors|accessdate = 2010-09-26|language=Russian}}</ref> which are both dedicated to the production of transcurium (''Z'' > 96) elements. These facilities have similar power and flux levels, and are expected to have comparable production capacities for transcurium elements,<ref name=h1582>[[#Haire|Haire]], p. 1582</ref> although the quantities produced at NIIAR are not widely reported. In a "typical processing campaign" at Oak Ridge, tens of grams of [[curium]] are irradiated to produce decigram quantities of [[californium]], milligram quantities of berkelium (<sup>249</sup>Bk) and einsteinium and picogram quantities of [[fermium]].<ref>[[#Greenwood|Greenwood]], p. 1262</ref><ref>{{cite journal|first1 = C. E.|last1 = Porter|first2 = F. D., Jr.|last2 = Riley|first3 = R. D.|last3 = Vandergrift|first4 = L. K.|last4 = Felker|title = Fermium Purification Using Teva Resin Extraction Chromatography|journal = Sep. Sci. Technol.|volume = 32|issue = 1–4|year = 1997|pages = 83–92|doi = 10.1080/01496399708003188}}</ref>
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| The first microscopic sample of <sup>253</sup>Es sample weighing about 10 [[nanogram]]s was prepared in 1961 at HFIR. A special magnetic balance was designed to estimate its weight.<ref name=CRC/><ref>Hoffman, Darleane C.; Ghiorso, Albert and Seaborg, Glenn Theodore (2000) ''The Transuranium People: The Inside Story'', Imperial College Press, pp. 190–191, ISBN 978-1-86094-087-3.</ref> Larger batches were produced later starting from several kilograms of plutonium with the einsteinium yields (mostly <sup>253</sup>Es) of 0.48 milligrams in 1967–1970, 3.2 milligrams in 1971–1973, followed by steady production of about 3 milligrams per year between 1974 and 1978.<ref name=s36>[[#Seaborg|Seaborg]], pp. 36–37</ref> These quantities however refer to the integral amount in the target right after irradiation. Subsequent separation procedures reduced the amount of isotopically pure einsteinium roughly tenfold.<ref name=h1582/>
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| ===Laboratory synthesis===
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| Heavy neutron irradiation of plutonium results in four major isotopes of einsteinium: <sup>253</sup>Es (α-emitter with half-life of 20.03 days and with a spontaneous fission half-life of 7×10<sup>5</sup> years); <sup>254''m''</sup>Es (β-emitter with half-life of 38.5 hours), <sup>254</sup>Es (α-emitter with half-life of about 276 days) and <sup>255</sup>Es (β-emitter with half-life of 24 days).<ref>{{cite journal|last1=Jones|first1=M.|last2=Schuman|first2=R.|last3=Butler|first3=J.|last4=Cowper|first4=G.|last5=Eastwood|first5=T.|last6=Jackson|first6=H.|title=Isotopes of Einsteinium and Fermium Produced by Neutron Irradiation of Plutonium|journal=Physical Review|volume=102|pages=203|year=1956|doi=10.1103/PhysRev.102.203|bibcode = 1956PhRv..102..203J }}</ref> An alternative route involves bombardment of uranium-238 with high-intensity nitrogen or oxygen ion beams.<ref>{{cite journal|last1=Guseva|first1=L|last2=Filippova|first2=K|last3=Gerlit|first3=Y|last4=Druin|first4=V|last5=Myasoedov|first5=B|last6=Tarantin|first6=N|title=Experiments on the production of einsteinium and fermium with a cyclotron|journal=Journal of Nuclear Energy (1954)|volume=3|pages=341|year=1956|doi=10.1016/0891-3919(56)90064-X|issue=4}}</ref>
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| Einsteinium-247 (half-life 4.55 minutes) was produced by irradiating americium-241 with carbon or uranium-238 with nitrogen ions.<ref name="Binder">Harry H. Binder: ''Lexikon der chemischen Elemente'', S. Hirzel Verlag, Stuttgart 1999, ISBN 3-7776-0736-3, pp. 18–23.</ref> The latter reaction was first realized in 1967 in Dubna, Russia, and the involved scientists were awarded the [[Lenin Komsomol Prize]].<ref>[http://n-t.ru/ri/ps/pb099.htm Эйнштейний] (in Russian, a popular article by one of the involved scientists)</ref>
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| The isotope <sup>248</sup>Es was produced by irradiating <sup>249</sup>Cf with [[deuterium]] ions. It mainly decays by emission of electrons to <sup>248</sup>Cf with a half-life of 25 (±5) minutes, but also releases α-particles of 6.87 MeV energy, with the ratio of electrons to α-particles of about 400.<ref>{{cite journal|last1=Chetham-Strode|first1=A.|last2=Holm|first2=L.|title=New Isotope Einsteinium-248|journal=Physical Review|volume=104|pages=1314|year=1956|doi=10.1103/PhysRev.104.1314|issue=5|bibcode = 1956PhRv..104.1314C }}</ref>
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| :<math>\mathrm{^{249}_{\ 98}Cf\ +\ ^{2}_{1}D\ \longrightarrow\ ^{248}_{\ 99}Es\ +\ 3\ ^{1}_{0}n \quad (^{248}_{\ 99}Es\ \xrightarrow[27 \ min]{\epsilon} \ ^{248}_{\ 98}Cf)}</math>
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| The heavier isotopes <sup>249</sup>Es, <sup>250</sup>Es, <sup>251</sup>Es and <sup>252</sup>Es were obtained by bombarding <sup>249</sup>Bk with α-particles. One to four neutrons are liberated in this process making possible the formation of four different isotopes in one reaction.<ref>{{cite journal|last1=Harvey|first1=Bernard|last2=Chetham-Strode|first2=Alfred|last3=Ghiorso|first3=Albert|last4=Choppin|first4=Gregory|last5=Thompson|first5=Stanley|title=New Isotopes of Einsteinium|journal=Physical Review|volume=104|pages=1315|year=1956|doi=10.1103/PhysRev.104.1315|issue=5|bibcode = 1956PhRv..104.1315H }}</ref>
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| :<math>\mathrm{^{249}_{\ 97}Bk\ \xrightarrow {+\alpha} \ ^{249,\ 250,\ 251,\ 252}_{\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ 99}Es}</math>
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| Einsteinium-253 was produced by irradiating a 0.1–0.2 milligram <sup>252</sup>Cf target with a [[thermal neutron]] flux of (2–5)×10<sup>14</sup> neutrons·cm<sup>−2</sup>·s<sup>−1</sup> for 500–900 hours:<ref>{{cite journal|last1=Kulyukhin|first1=S|title=Production of microgram quantities of einsteinium-253 by the reactor irradiation of californium|journal=Inorganica Chimica Acta|volume=110|pages=25|year=1985|doi=10.1016/S0020-1693(00)81347-X|last2=Auerman|first2=L.N.|last3=Novichenko|first3=V.L.|last4=Mikheev|first4=N.B.|last5=Rumer|first5=I.A.|last6=Kamenskaya|first6=A.N.|last7=Goncharov|first7=L.A.|last8=Smirnov|first8=A.I.}}</ref>
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| :<math>\mathrm{^{252}_{\ 98}Cf\ \xrightarrow {(n,\gamma)} \ ^{253}_{\ 98}Cf\ \xrightarrow [17.81 \ d]{\beta^-} \ ^{253}_{\ 99}Es}</math>
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| ===Synthesis in nuclear explosions===
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| [[File:ActinideExplosionSynthesis.png|thumb|300px|left|Estimated yield of transuranium elements in the U.S. nuclear tests Hutch and Cyclamen.<ref name=s40/>]]
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| The analysis of the debris at the 10-[[TNT equivalent|megaton]] ''Ivy Mike'' nuclear test was a part of long-term project. One of the goals of which was studying the efficiency of production of transuranium elements in high-power nuclear explosions. The motivation for these experiments was that synthesis of such elements from uranium requires multiple neutron capture. The probability of such events increases with the [[neutron flux]], and nuclear explosions are the most powerful man-made neutron sources, providing densities of the order 10<sup>23</sup> neutrons/cm² within a microsecond, or about 10<sup>29</sup> neutrons/(cm²·s). In comparison, the flux of the HFIR reactor is 5{{e|15}} neutrons/(cm²·s). A dedicated laboratory was set up right at [[Enewetak Atoll]] for preliminary analysis of debris, as some isotopes could have decayed by the time the debris samples reached the mainland U.S. The laboratory was receiving samples for analysis as soon as possible, from airplanes equipped with paper filters which flew over the atoll after the tests. Whereas it was hoped to discover new chemical elements heavier than fermium, none of these were found even after a series of megaton explosions conducted between 1954 and 1956 at the atoll.<ref name=s39/>
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| The atmospheric results were supplemented by the underground test data accumulated in the 1960s at the [[Nevada National Security Site|Nevada Test Site]], as it was hoped that powerful explosions conducted in confined space might result in improved yields and heavier isotopes. Apart from traditional uranium charges, combinations of uranium with americium and [[thorium]] have been tried, as well as a mixed plutonium-neptunium charge, but they were less successful in terms of yield and was attributed to stronger losses of heavy isotopes due to enhanced fission rates in heavy-element charges. Product isolation was problematic as the explosions were spreading debris through melting and vaporizing the surrounding rocks at depths of 300–600 meters. Drilling to such depths to extract the products was both slow and inefficient in terms of collected volumes.<ref name=s39/><ref name=s40>[[#Seaborg|Seaborg]], p. 40</ref>
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| Among the nine underground tests that were carried between 1962 and 1969,<ref>These were codenamed: "Anacostia" (5.2 [[TNT equivalent|kilotons]], 1962), "Kennebec" (<5 kilotons, 1963), "Par" (38 kilotons, 1964), "Barbel" (<20 kilotons, 1964), "Tweed" (<20 kilotons, 1965), "Cyclamen" (13 kilotons, 1966), "Kankakee" (20-200 kilotons, 1966), "Vulcan" (25 kilotons, 1966) and "Hutch" (20-200 kilotons, 1969)</ref><ref>[http://www.nv.doe.gov/library/publications/historical/DOENV_209_REV15.pdf United States Nuclear Tests July 1945 through September 1992], DOE/NV--209-REV 15, December 2000.</ref> the last one was the most powerful and had the highest yield of transuranium elements. Milligrams of einsteinium that would normally take a year of irradiation in a high-power reactor, were produced within a microsecond.<ref name=s40/> However, the major practical problem of the entire proposal was collecting the radioactive debris dispersed by the powerful blast. Aircraft filters adsorbed only about 4{{e|-14}} of the total amount, and collection of tons of corals at Enewetak Atoll increased this fraction by only two orders of magnitude. Extraction of about 500 kilograms of underground rocks 60 days after the Hutch explosion recovered only about 1{{e|-7}} of the total charge. The amount of transuranium elements in this 500-kg batch was only 30 times higher than in a 0.4 kg rock picked up 7 days after the test which demonstrated the highly non-linear dependence of the transuranium elements yield on the amount of retrieved radioactive rock.<ref name=s43>[[#Seaborg|Seaborg]], p. 43</ref> Shafts were drilled at the site before the test in order to accelerate sample collection after explosion, so that explosion would expel radioactive material from the epicenter through the shafts and to collecting volumes near the surface. This method was tried in two tests and instantly provided hundreds kilograms of material, but with actinide concentration 3 times lower than in samples obtained after drilling. Whereas such method could have been efficient in scientific studies of short-lived isotopes, it could not improve the overall collection efficiency of the produced actinides.<ref name=s44>[[#Seaborg|Seaborg]], p. 44</ref>
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| Although no new elements (apart from einsteinium and fermium) could be detected in the nuclear test debris, and the total yields of transuranium elements were disappointingly low, these tests did provide significantly higher amounts of rare heavy isotopes than previously available in laboratories.<!-- About 6{{e|9}} atoms of <sup>257</sup>Fm could be recovered after the Hutch detonation. These were then used in the studies of thermal-neutron induced fission of <sup>257</sup>Fm, and in discovery of a new fermium isotope. <sup>258</sup>Fm. Also, the rare <sup>250</sup>Cm isotope was synthesized in large quantities, which would have been otherwise very difficult to produce in nuclear reactors from its progenitor <sup>249</sup>Cm – the half-life of <sup>249</sup>Cm (64 minutes) is much too short for months-long reactor irradiations, but is very "long" on the timescale of an explosion.--><ref name=s47>[[#Seaborg|Seaborg]], p. 47</ref>
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| ===Separation===
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| [[File:Elutionskurven Fm Es Cf Bk Cm Am.png|thumb|[[Elution]] curves: chromatographic separation of Fm(100), Es(99), Cf, Bk, Cm and Am]]
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| Separation procedure of einsteinium depends on the synthesis method. In the case of light-ion bombardment inside a cyclotron, the heavy ion target is attached to a thin foil, and the generated einsteinium is simply washed off the foil after the irradiation. However, the produced amounts in such experiments are relatively low.<ref name=h1583>[[#Haire|Haire]], p. 1583</ref> The yields are much higher for reactor irradiation, but there, the product is a mixture of various actinide isotopes, as well as lanthanides produced in the nuclear fission decays. In this case, isolation of einsteinium is a tedious procedure which involves several repeating steps of cation exchange, at elevated temperature and pressure, and chromatography. Separation from berkelium is important, because the most common einsteinium isotope produced in nuclear reactors, <sup>253</sup>Es, decays with a half-life of only 20 days to <sup>249</sup>Bk, which is fast on the timescale of most experiments. Such separation relies on the fact that berkelium easily oxidizes to the solid +4 state and precipitates, whereas other actinides, including einsteinium, remain in their +3 state in solutions.<ref name=h1584>[[#Haire|Haire]], pp. 1584–1585</ref>
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| Separation of trivalent actinides from lanthanide fission products can be done by a cation-exchange resin column using a 90% water/10% ethanol solution saturated with [[hydrochloric acid]] (HCl) as [[eluant]]. It is usually followed by anion-exchange chromatography using 6 [[molar concentration|molar]] HCl as eluant. A cation-exchange resin column (Dowex-50 exchange column) treated with ammonium salts is then used to separate fractions containing elements 99, 100 and 101. These elements can be then identified simply based on their elution position/time, using α-hydroxyisobutyrate solution (α-HIB), for example, as eluant.<ref name=book2>{{cite book|url=http://books.google.com/books?id=U4rnzH9QbT4C&pg=PA11|pages=9–11|title=The new chemistry|author=Hall, Nina|publisher=Cambridge University Press|year=2000|isbn=0-521-45224-4}}</ref>
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| Separation of the 3+ actinides can also be achieved by solvent extraction chromatography, using bis-(2-ethylhexyl) phosphoric acid (abbreviated as HDEHP) as the stationary organic phase, and nitric acid as the mobile aqueous phase. The actinide elution sequence is reversed from that of the cation-exchange resin column. The einsteinium separated by this method has the advantage to be free of organic complexing agent, as compared to the separation using a resin column.<ref name=book2/>
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| ===Preparation of the metal===
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| Einsteinium is highly reactive and therefore strong reducing agents are required to obtain the pure metal from its compounds.<ref name=h1588>[[#Haire|Haire]], p. 1588</ref> This can be achieved by reduction of einsteinium(III) fluoride with metallic [[lithium]]:
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| :EsF<sub>3</sub> + 3 Li → Es + 3 LiF
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| However, owing to its low melting point and high rate of self-radiation damage, einsteinium has high vapor pressure, which is higher than that of lithium fluoride. This makes this reduction reaction rather inefficient. It was tried in the early preparation attempts and quickly abandoned in favor of reduction of einsteinium(III) oxide with [[lanthanum]] metal:<ref name=ev>{{cite journal|last1=Haire|first1=R|title=Preparation, properties, and some recent studies of the actinide metals|url=http://www.osti.gov/bridge/product.biblio.jsp?osti_id=5235830|doi=10.1016/0022-5088(86)90554-0|year=1986|pages=379|volume=121|journal=Journal of the Less Common Metals}}</ref><ref name="ES_METALL"/><ref name=h1590>[[#Haire|Haire]], p. 1590</ref>
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| :Es<sub>2</sub>O<sub>3</sub> + 2 La → 2 Es + La<sub>2</sub>O<sub>3</sub>
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| ==Chemical compounds==
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| {|class = "wikitable collapsible collapsed"
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| |+Crystal structure and lattice constants of some Es compounds
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| !Compound!!Color !! Symmetry!![[Space group]]!!No!![[Pearson symbol]]||''a'' ([[picometer|pm]])!!''b'' (pm)!!''c'' (pm)
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| |Es<sub>2</sub>O<sub>3</sub>|| Colorless||Cubic<ref name="ES2O3"/>||Ia{{overline|3}}|| 206||cI80||1076.6|| ||
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| |Es<sub>2</sub>O<sub>3</sub>|| Colorless||[[Monoclinic crystal system|Monoclinic]]<ref name=ox1/>||C2/m||12|| mS30||1411||359 || 880
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| |Es<sub>2</sub>O<sub>3</sub>|| Colorless||Hexagonal<ref name=ox1/>|| P{{overline|3}}m1||164 ||hP5||370|| ||600
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| |EsF<sub>3</sub>|| ||Hexagonal<ref name="ES_F3"/>|| || || || || ||
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| |EsF<sub>4</sub>|| ||Monoclinic<ref>{{cite journal|last1=Kleinschmidt|first1=P|title=Thermochemistry of the actinides|journal=Journal of Alloys and Compounds|volume=213–214|pages=169|year=1994|doi=10.1016/0925-8388(94)90898-2}}</ref> || C2/c||15 ||mS60 || || ||
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| |EsCl<sub>3</sub>||Orange||Hexagonal<ref>{{cite journal|last1=Fujita|first1=D|title=Crystal structures and lattice parameters of einsteinium trichloride and einsteinium oxychloride|journal=Inorganic and Nuclear Chemistry Letters|volume=5|pages=307|year=1969|doi=10.1016/0020-1650(69)80203-5|issue=4|last2=Cunningham|first2=B.B.|last3=Parsons|first3=T.C.}}</ref><ref name=m99/>|| C6<sub>3</sub>/m|| ||hP8 ||727 || ||410
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| |EsBr<sub>3</sub>||Yellow||Monoclinic<ref>{{cite journal|last1=Fellows|first1=R|title=X-ray diffraction and spectroscopic studies of crystalline einsteinium(III) bromide, <sup>253</sup>EsBr<sub>3</sub>|journal=Inorganic and Nuclear Chemistry Letters|volume=11|pages=737|year=1975|doi=10.1016/0020-1650(75)80090-0|issue=11|last2=Peterson|first2=J.R.|last3=Noé|first3=M.|last4=Young|first4=J.P.|last5=Haire|first5=R.G.}}</ref>||C2/m || 12|| mS16||727 ||1259 || 681
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| |EsI<sub>3</sub>||Amber||Hexagonal<ref name=h1595/><ref name=s62>[[#Seaborg|Seaborg]], p. 62</ref>||R{{overline|3}} ||148 ||hR24 || 753|| ||2084
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| |EsOCl|| ||Tetragonal<ref name=h1595>[[#Haire|Haire]], pp. 1595–1596</ref><ref name="YOUNG_1981"/>|| P4/nmm|| || ||394.8 || || 670.2
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| |}
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| ===Oxides===
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| Einsteinium(III) oxide (Es<sub>2</sub>O<sub>3</sub>) was obtained by burning einsteinium(III) nitrate. It forms colorless cubic crystals, which were first characterized from microgram samples sized about 30 nanometers.<ref name=g1268>[[#Greenwood|Greenwood]], p. 1268</ref><ref name="ES2O3">{{cite journal|last1=Haire|first1=R.G.|last2=Baybarz|first2=R.D.|title=Identification and analysis of einsteinium sesquioxide by electron diffraction|journal=Journal of Inorganic and Nuclear Chemistry|volume=35|pages=489|year=1973|doi=10.1016/0022-1902(73)80561-5|issue=2}}</ref> Two other phases, [[Monoclinic crystal system|monoclinic]] and hexagonal, are known for this oxide. The formation of a certain Es<sub>2</sub>O<sub>3</sub> phase depends on the preparation technique and sample history, and there is no clear phase diagram. Interconversions between the three phases can occur spontaneously, as a result of self-irradiation or self-heating.<ref name=h1598>[[#Haire|Haire]], p. 1598</ref> The hexagonal phase is isotypic with [[lanthanum(III) oxide]] where the Es<sup>3+</sup> ion is surrounded by a 6-coordinated group of O<sup>2–</sup> ions.<ref name=ox1>{{cite book|title=Handbook on the Physics and Chemistry of Rare Earths|volume=18|chapter=Lanthanides and Actinides Chemistry|editors=K.A. Gscheidner, Jr. ''et al.''|location=North-Holland, New York|year=1994|pages=414–505|isbn=0-444-81724-7|author=Haire, R. G. and Eyring, L.}}</ref><ref name=h1595/>
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| ===Halides===
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| [[File:Einsteinium triiodide by transmitted light.jpg|thumb|[[Einsteinium(III) iodide]] glowing in the dark]]
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| Einsteinium [[halide]]s are known for the oxidation states +2 and +3.<ref Name="YOUNG_1981">{{cite journal|last1=Young|first1=J. P.|last2=Haire|first2=R. G.|last3=Peterson|first3=J. R.|last4=Ensor|first4=D. D.|last5=Fellow|first5=R. L.|title=Chemical consequences of radioactive decay. 2. Spectrophotometric study of the ingrowth of berkelium-249 and californium-249 into halides of einsteinium-253|journal=Inorganic Chemistry|volume=20|pages=3979|year=1981|doi=10.1021/ic50225a076|issue=11}}</ref><ref name = "HOWI_1969">[[#Holleman|Holleman]], p. 1969</ref> The most stable state is +3 for all halides from fluoride to iodide.
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| Einsteinium(III) fluoride (EsF<sub>3</sub>) can be precipitated from einsteinium(III) chloride solutions upon reaction with [[fluoride]] ions. An alternative preparation procedure is to exposure einsteinium(III) oxide to [[chlorine trifluoride]] (ClF<sub>3</sub>) or F<sub>2</sub> gas at a pressure of 1–2 atmospheres and a temperature between 300 and 400 °C. The EsF<sub>3</sub> crystal structure is hexagonal, as in californium(III) fluoride (CfF<sub>3</sub>) where the Es<sup>3+</sup> ions are 8-fold coordinated by fluorine ions in a bicapped [[Octahedral molecular geometry#Trigonal prismatic geometry|trigonal prism]] arrangement.<ref name="ES_F3">{{cite journal|last1=Ensor|first1=D.D.|last2=Peterson|first2=J.R.|last3=Haire|first3=R.G.|last4=Young|first4=J.P.|title=Absorption spectrophotometric study of <sup>253</sup>EsF<sub>3</sub> and its decay products in the bulk-phase solid state|journal=Journal of Inorganic and Nuclear Chemistry|volume=43|pages=2425|year=1981|doi=10.1016/0022-1902(81)80274-6|issue=10}}</ref><ref name=g1270>[[#Greenwood|Greenwood]], p. 1270</ref><ref>{{cite journal|last1=Young|first1=J. P.|last2=Haire|first2=R. G.|last3=Fellows|first3=R. L.|last4=Peterson|first4=J. R.|title=Spectrophotometric studies of transcurium element halides and oxyhalides in the solid state|journal=Journal of Radioanalytical Chemistry|volume=43|pages=479|year=1978|doi=10.1007/BF02519508|issue=2}}</ref>
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| Einsteinium(III) chloride (EsCl<sub>3</sub>) can be prepared by annealing einsteinium(III) oxide in the atmosphere of dry hydrogen chloride vapors at about 500 °C for some 20 minutes. It crystallizes upon cooling at about 425 °C into an orange solid with a [[hexagonal crystal system|hexagonal]] structure of [[uranium(III) chloride|UCl</sub>3</sub> type]], where einsteinium atoms are 9-fold coordinated by chlorine atoms in a tricapped trigonal prism geometry.<ref name=m99>Miasoedov, B. F. Analytical chemistry of transplutonium elements, Wiley, 1974 (Original from the University of California), ISBN 0-470-62715-8, p. 99</ref><ref name=g1270/><ref>{{cite journal|last1=Fujita|first1=D|title=The solution absorption spectrum of Es<sup>3+</sup>|journal=Inorganic and Nuclear Chemistry Letters|volume=5|pages=245|year=1969|doi=10.1016/0020-1650(69)80192-3|issue=4|last2=Cunningham|first2=B.B.|last3=Parsons|first3=T.C.|last4=Peterson|first4=J.R.}}</ref> Einsteinium(III) bromide (EsBr<sub>3</sub>) is a pale-yellow solid with a [[Monoclinic crystal system|monoclinic]] structure of [[aluminum chloride|AlCl<sub>3</sub> type]], where the einsteinium atoms are [[Octahedral molecular geometry|octahedrally]] coordinated by bromine (coordination number 6).<ref name=s62/><ref name=g1270/>
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| The divalent compounds of einsteinium are obtained by reducing the trivalent halides with [[hydrogen]]:<ref Name="ES_II">{{cite journal|url=http://hal.archives-ouvertes.fr/docs/00/21/88/31/PDF/ajp-jphyscol197940C435.pdf|title=Preparation, characterization, and decay of einsteinium(II) in the solid state|journal=Le Journal de Physique|author=Peterson, J.R. ''et al.''|volume=40|issue=4|page=C4–111|year=1979}} [http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=6593662 manuscript draft]</ref>
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| :2 EsX<sub>3</sub> + H<sub>2</sub> → 2 EsX<sub>2</sub> + 2 HX, X = F, Cl, Br, I
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| Einsteinium(II) chloride (EsCl<sub>2</sub>),<ref>Fellows, R.L.; Young, J.P.; Haire, R.G. and Peterson J.R. (1977) in: GJ McCarthy and JJ Rhyne (eds) ''The Rare Earths in Modern Science and Technology'', Plenum Press, New York, pp. 493–499.</ref> einsteinium(II) bromide (EsBr<sub>2</sub>),<ref>Young, J.P.; Haire R.G., Fellows, R.L.; Noe, M. and Peterson, J.R. (1976) "Spectroscopic and X-Ray Diffraction Studies of the Bromides of Californium-249 and Einsteinium-253", in: W. Müller and R. Lindner (eds.) ''Plutonium 1975'', North Holland, Amsterdam, pp. 227–234.</ref> and einsteinium(II) iodide (EsI<sub>2</sub>)<ref name = "YOUNG_1981" /> have been produced and characterized by optical absorption, with no structural information available yet.<ref name=s62/>
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| Known oxyhalides of einsteinium include EsOCl,<ref name="YOUNG_1981"/> EsOBr<ref name="ES_II"/> and EsOI.<ref name="YOUNG_1981"/> They are synthesized by treating a trihalide with a vapor mixture of water and the corresponding hydrogen halide: for example, EsCl<sub>3</sub> + H<sub>2</sub>O/HCl to obtain EsOCl.<ref name=s60>[[#Seaborg|Seaborg]], p. 60</ref>
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| ===Organoeinsteinium compounds===
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| The high radioactivity of einsteinium has a potential use in [[radiation therapy]], and organometallic complexes have been synthesized in order to deliver einsteinium atoms to an appropriate organ in the body. Experiments have been performed on injecting einsteinium [[citrate]] (as well as fermium compounds) to dogs.<ref name=h1579/> Einsteinium(III) was also incorporated into beta-diketone [[Chelation|chelate]] complexes, since analogous complexes with lanthanides previously showed strongest UV-excited [[luminescence]] among metallorganic compounds. When preparing einsteinium complexes, the Es<sup>3+</sup> ions were 1000 times diluted with Gd<sup>3+</sup> ions. This allowed reducing the radiation damage so that the compounds did not disintegrate during the period of 20 minutes required for the measurements. The resulting luminescence from Es<sup>3+</sup> was much too weak to be detected. This was explained by the unfavorable relative energies of the individual constituents of the compound that hindered efficient energy transfer from the chelate matrix to Es<sup>3+</sup> ions. Similar conclusion was drawn for other actinides americium, berkelium and fermium.<ref>{{cite journal|last1=Nugent|first1=Leonard J.|last2=Burnett|first2=J. L.|last3=Baybarz|first3=R. D.|last4=Werner|first4=George Knoll|last5=Tanner|first5=S. P.|last6=Tarrant|first6=J. R.|last7=Keller|first7=O. L.|title=Intramolecular energy transfer and sensitized luminescence in actinide(III) .beta.-diketone chelates|journal=The Journal of Physical Chemistry|volume=73|pages=1540|year=1969|doi=10.1021/j100725a060|issue=5}}</ref>
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| Luminescence of Es<sup>3+</sup> ions was however observed in inorganic hydrochloric acid solutions as well as in organic solution with di(2-ethylhexyl)orthophosphoric acid. It shows a broad peak at about 1064 nanometers (half-width about 100 nm) which can be resonantly excited by green light (ca. 495 nm wavelength). The luminescence has a lifetime of several microseconds and the quantum yield below 0.1%. The relatively high, compared to lanthanides, non-radiative decay rates in Es<sup>3+</sup> were associated with the stronger interaction of f-electrons with the inner Es<sup>3+</sup> electrons.<ref>{{cite journal|last1=Beitz|first1=J|last2=Wester|first2=D|last3=Williams|first3=C|title=5f state interaction with inner coordination sphere ligands: Es<sup>3+</sup> ion fluorescence in aqueous and organic phases|journal=Journal of the Less Common Metals|volume=93|pages=331|year=1983|doi=10.1016/0022-5088(83)90178-9|issue=2}}</ref>
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| ==Applications==
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| There is almost no use for any isotope of einsteinium outside of basic scientific research aiming at production of higher [[transuranic elements]] and [[transactinides]].<ref>[http://education.jlab.org/itselemental/ele099.html It's Elemental – The Element Einsteinium]. Retrieved 2 December 2007.</ref>
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| In 1955, mendelevium was synthesized by irradiating a target consisting of about 10<sup>9</sup> atoms of <sup>253</sup>Es in the 60-inch cyclotron at Berkeley Laboratory. The resulting <sup>253</sup>Es(α,n)<sup>256</sup>Md reaction yielded 17 atoms of the new element with the atomic number of 101.<ref name=discovery>{{cite journal|doi=10.1103/PhysRev.98.1518|url=http://books.google.com/books?id=e53sNAOXrdMC&pg=PA101|isbn=978-981-02-1440-1|title=New Element Mendelevium, Atomic Number 101|year=1955|last1=Ghiorso|first1=A.|last2=Harvey|first2=B.|last3=Choppin|first3=G.|last4=Thompson|first4=S.|last5=Seaborg|first5=G.|journal=Physical Review|volume=98|pages=1518|issue=5|bibcode = 1955PhRv...98.1518G }}</ref>
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| The rare isotope [[einsteinium-254]] is favored for production of [[superheavy element|ultraheavy elements]] because of its large mass, relatively long half-life of 270 days, and availability in significant amounts of several micrograms.<ref>{{cite journal|last1=Schadel|first1=M|last2=Bruchle|first2=W|last3=Brugger|first3=M|last4=Gaggeler |first4=H|last5=Moody|first5=K|last6=Schardt|first6=D|last7=Summerer|first7=K|last8=Hulet|first8=E|last9=Dougan|first9=A|first10=R |last10=Dougan|first11=J |last11=Landrum|first12=R |last12=Lougheed|first13=J |last13=Wild|first14=G |last14=O'Kelley|first15=R |last15=Hahn
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| |title=Heavy isotope production by multinucleon transfer reactions with <sup>254</sup>Es|journal=Journal of the Less Common Metals|volume=122|pages=411|year=1986|doi=10.1016/0022-5088(86)90435-2}}</ref> Hence einsteinium-254 was used as a target in the attempted synthesis of [[ununennium]] (element 119) in 1985 by bombarding it with calcium-48 ions at the superHILAC [[linear accelerator]] at Berkeley, California. No atoms were identified, setting an upper limit for the cross section of this reaction at 300 [[barn (unit)|nanobarns]].<ref>{{cite journal|title=Search for superheavy elements using <sup>48</sup>Ca + <sup>254</sup>Es<sup>g</sup> reaction|author=Lougheed, R. W.; Landrum, J. H.; Hulet, E. K.; Wild, J. F.; Dougan, R. J.; Dougan, A. D.; Gäggeler, H.; Schädel, M.; Moody, K. J.; Gregorich, K. E. and Seaborg, G. T.|journal=Physical Reviews C|year=1985|pages=1760–1763|doi=10.1103/PhysRevC.32.1760|volume=32|issue=5|bibcode = 1985PhRvC..32.1760L }}</ref>
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| :<math>\,^{254}_{99}\mathrm{Es} + \,^{48}_{20}\mathrm{Ca} \to \,^{302}_{119}\mathrm{Uue} ^{*} \to \
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| \ no\ atoms</math>
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| Einsteinium-254 was used as the calibration marker in the chemical analysis spectrometer ("[[Surveyor 5#Alpha-scattering surface analyzer|alpha-scattering surface analyzer]]") of the [[Surveyor 5]] lunar probe. The large mass of this isotope reduced the spectral overlap between signals from the marker and the studied lighter elements of the lunar surface.<ref>{{cite journal|doi=10.1126/science.158.3801.635|title=Chemical Analysis of the Moon at the Surveyor V Landing Site|year=1967|last1=Turkevich|first1=A. L.|last2=Franzgrote|first2=E. J.|last3=Patterson|first3=J. H.|journal=Science|volume=158|issue=3801|pages=635–637|pmid=17732956|bibcode = 1967Sci...158..635T }}</ref>
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| ==Safety==
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| Most of the available einsteinium toxicity data originates from research on animals. Upon ingestion by rats, only about 0.01% einsteinium ends in the blood stream. From there, about 65% goes to the bones, where it remains for about 50 years, 25% to the lungs (biological half-life about 20 years, although this is rendered irrelevant by the short half-lives of einsteinium isotopes), 0.035% to the testicles or 0.01% to the ovaries – where einsteinium stays indefinitely. About 10% of the ingested amount is excreted. The distribution of einsteinium over the bone surfaces is uniform and is similar to that of plutonium.<ref>{{cite book|author=International Commission on Radiological Protection|title=Limits for intakes of radionuclides by workers, Part 4, Volume 19, Issue 4|url=http://books.google.com/books?id=WTxcCV4w0VEC&pg=PA18|isbn=0-08-036886-7|publisher=Elsevier Health Sciences|year=1988|pages=18–19}}</ref>
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| ==References==
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| {{reflist|2}}
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| ==Bibliography==
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| * {{cite book|ref=Greenwood|author=Greenwood, Norman N.; Earnshaw, Alan |year=1997|title=Chemistry of the Elements |edition=2nd |publisher=Butterworth–Heinemann|isbn=0080379419}}
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| * {{cite book|first = Richard G.|last = Haire|ref=Haire|contribution = Einsteinium|title = The Chemistry of the Actinide and Transactinide Elements|editor1-first = Lester R.|editor1-last = Morss|editor2-first = Norman M.|editor2-last = Edelstein|editor3-first = Jean|editor3-last = Fuger|edition = 3rd|year = 2006|volume = 3|publisher = Springer|location = Dordrecht, the Netherlands|pages = 1577–1620|url = http://radchem.nevada.edu/classes/rdch710/files/einsteinium.pdf|doi = 10.1007/1-4020-3598-5_12}}
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| * {{cite book|ref=Holleman|author=Holleman, Arnold F. and Wiberg, Nils |title=Textbook of Inorganic Chemistry|edition= 102 ed.|publisher=de Gruyter|place= Berlin |year=2007|isbn=978-3-11-017770-1}}
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| *{{cite book|ref=Seaborg|editor= Seaborg, G.T. |year=1978|url=http://www.escholarship.org/uc/item/92g2p7cd.pdf |title=Proceedings of the Symposium Commemorating the 25th Anniversary of Elements 99 and 100|date=23 January 1978|publisher=Report LBL-7701}}
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| ==External links==
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| {{Commons|Einsteinium}}
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| {{wiktionary|einsteinium}}
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| * [http://www.periodicvideos.com/videos/099.htm Einsteinium] at ''[[The Periodic Table of Videos]]'' (University of Nottingham)
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| * [http://books.google.com/books?id=cgqNoNWLGBMC&pg=PA311 Age-related factors in radionuclide metabolism and dosimetry: Proceedings] – contains several health related studies of einsteinium
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| {{clear}}
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| {{compact periodic table}}
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| {{Chemical elements named after scientists}}
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| [[Category:Chemical elements]]
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| [[Category:Actinides]]
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| [[Category:Synthetic elements]]
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| [[Category:Einsteinium]]
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| {{Link GA|de}}
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| {{Link GA|zh}}
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