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| [[File:Berkelium(IV) oxide.jpg|thumb|250px|Berkelium(IV) oxide]]
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| [[Berkelium]] forms a number of [[chemical compound]]s, where it normally exists in an [[Oxidation number|oxidation state]] of +3 or +4, and behaves similarly to its [[lanthanide]] analogue, [[terbium]].<ref name=c1>{{cite journal|doi=10.2172/932812|last1=Thompson|year=1950|first1=Stanley G.|last2=Seaborg|first2=Glenn T.|url=http://www.osti.gov/bridge/purl.cover.jsp?purl=/932812-Rk9Mcq/}}</ref> Like all actinides, berkelium easily dissolves in various [[aqueous solution|aqueous inorganic acids]], liberating gaseous [[hydrogen]] and converting into the trivalent oxidation state. This trivalent state is the most stable, especially in [[aqueous solution]]s, but tetravalent berkelium compounds are also known. The existence of divalent berkelium salts is uncertain and has only been reported in mixed [[lanthanum chloride]]-[[strontium chloride]] melts.<ref name=e55/><ref>{{cite journal|last1=Sullivan|first1=Jim C.|last2=Schmidt|first2=K. H.|last3=Morss|first3=L. R.|last4=Pippin|first4=C. G.|last5=Williams|first5=C.|title=Pulse radiolysis studies of berkelium(III): preparation and identification of berkelium(II) in aqueous perchlorate media|journal=Inorganic Chemistry|volume=27|pages=597|year=1988|doi=10.1021/ic00277a005}}</ref> Aqueous solutions of Bk<sup>3+</sup> ions are green in most acids. The color of the Bk<sup>4+</sup> ions is yellow in hydrochloric acid and orange-yellow in sulfuric acid.<ref name=e55>Peterson, p. 55</ref><ref name="HOWI_1956">Holleman, p. 1956</ref><ref>Greenwood, p. 1265</ref> Berkelium does not react rapidly with [[oxygen]] at room temperature, possibly due to the formation of a protective oxide surface layer; however, it reacts with molten metals, [[hydrogen]], [[halogen]]s, [[chalcogen]]s and [[pnictogen]]s to form various binary compounds.<ref name="H&P">{{cite book|first1 = David E.|last1 = Hobart|first2 = Joseph R.|last2 = Peterson|contribution = Berkelium|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 = 1444–98|url = http://radchem.nevada.edu/classes/rdch710/files/berkelium.pdf|doi = 10.1007/1-4020-3598-5_10}}</ref><ref name=e45>Peterson, p. 45</ref> Berkelium can also form several [[organometallic compound]]s.
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| ==Oxides==
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| Two oxides of berkelium are known, with berkelium in the +3 (Bk<sub>2</sub>O<sub>3</sub>) and +4 (BkO<sub>2</sub>) oxidation states.<ref>{{cite journal|last1=Peterson|first1=J|title=Crystal structures and lattice parameters of the compounds of berkelium I. Berkelium dioxide and cubic berkelium sesquioxide|journal=Inorganic and Nuclear Chemistry Letters|volume=3|pages=327|year=1967|doi=10.1016/0020-1650(67)80037-0}}</ref> Berkelium(IV) oxide is a brown solid that crystallizes in a cubic ([[fluorite]]) crystal structure with the [[space group]] ''Fm{{overline|3}}m'' and the [[coordination number]]s of Bk[8] and O[4]. The lattice parameter is 533.4 ± 0.5 [[picometer|pm]].<ref name="BK_OX">{{cite journal|last1=Baybarz|first1=R.D.|title=The berkelium oxide system|journal=Journal of Inorganic and Nuclear Chemistry|volume=30|pages=1769|year=1968|doi=10.1016/0022-1902(68)80352-5}}</ref>
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| [[Berkelium(III) oxide]], a yellow-green solid, is formed from BkO<sub>2</sub> by [[redox|reduction]] with hydrogen:
| | Fredrick is how I'm known as and I believe it sounds fairly good when you say it. The occupation I've been occupying for many years is a supervisor but quickly I'll be on my personal. What me and my family members love is bee keeping and I would by no means give it up. Wyoming is where I've usually been living and I don't plan on changing it. See what's new on my website here: http://isabeldeloitte.pen.io/<br><br>My web site: [http://isabeldeloitte.pen.io/ Delhi University] |
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| :<math>\mathrm{2\ BkO_2\ +\ H_2\ \longrightarrow \ Bk_2O_3\ +\ H_2O}</math>
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| The compound has a melting point of 1920 °C,<ref name="HOWI_1972">Holleman, p. 1972</ref> body-centered cubic crystal lattice and a lattice constant ''a'' = 1088.0 ± 0.5 pm.<ref name="BK_OX"/> Upon heating to 1200 °C, the cubic Bk<sub>2</sub>O<sub>3</sub> transforms to a monoclinic structure, which further converts to a hexagonal phase at 1750 °C; the latter transition is reversible. Such three-phase behavior is typical for the actinide [[sesquioxide]]s.<ref name=e51>Peterson, p. 51</ref>
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| A divalent oxide BkO has been reported as a brittle gray solid with a [[Cubic crystal system|face centered cubic]] (''fcc'') structure and a lattice constant ''a'' = 496.4 pm, but its exact chemical composition is uncertain.<ref name=e51/>
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| ==Halides==
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| In [[halide]]s, berkelium assumes the oxidation states +3 and +4.<ref name="HOWI_1969">Holleman, p. 1969</ref> The +3 state is most stable, especially in solutions, and the tetravalent halides BkF<sub>4</sub> and Cs<sub>2</sub>BkCl<sub>6</sub> are only known in the solid phase.<ref name=e47>Peterson, p. 47</ref> The coordination of the berkelium atom in its trivalent fluoride and chloride is tricapped [[Octahedral molecular geometry#Trigonal prismatic geometry|trigonal prismatic]], with a [[coordination number]] of 9. In the trivalent bromide, it is bicapped trigonal prismatic (coordination 8) or [[Octahedral molecular geometry|octahedral]] (coordination 6),<ref name=conv/> and in the iodide it is octahedral.<ref name=g1270/>
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| {| Class = "wikitable" style ="text-align: center"
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| |-
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| ! Oxidation number
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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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| ! +3
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| | [[Berkelium(III) fluoride]] <br /> BkF<sub>3</sub><br /> Yellow<ref name=g1270/>
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| | [[Berkelium(III) chloride]] <br /> BkCl<sub>3</sub><br /> Green<ref name=g1270/><br />Cs<sub>2</sub>NaBkCl<sub>6</sub><ref name=e48/>
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| | [[Berkelium(III) bromide]]<ref name=conv>{{cite journal|last1=Young|first1=J. P.|last2=Haire|first2=R. G.|last3=Peterson|first3=J. R.|last4=Ensor|first4=D. D.|last5=Fellows|first5=R. L.|title=Chemical consequences of radioactive decay. 1. Study of californium-249 ingrowth into crystalline berkelium-249 tribromide: a new crystalline phase of californium tribromide|journal=Inorganic Chemistry|volume=19|pages=2209|year=1980|doi=10.1021/ic50210a003}}</ref><ref>{{cite journal|last1=Burns|first1=J|title=Crystallographic studies of some transuranic trihalides: 239PuCl3, 244CmBr3, 249BkBr3 and 249CfBr3|journal=Journal of Inorganic and Nuclear Chemistry|volume=37|pages=743|year=1975|doi=10.1016/0022-1902(75)80532-X}}</ref><br />BkBr<sub>3</sub><br />Yellow-green<ref name=g1270/>
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| | [[Berkelium(III) iodide]] <br /> BkI<sub>3</sub><br /> Yellow<ref name=g1270/>
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| ! +4
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| | [[Berkelium(IV) fluoride]] <br /> BkF<sub>4</sub><br /> Yellow<ref name=g1270>Greenwood, p. 1270</ref>
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| | Cs<sub>2</sub>BkCl<sub>6</sub><br />Orange<ref name=e51/>
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| |}
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| Berkelium(IV) fluoride (BkF<sub>4</sub>) is a yellow-green ionic solid which crystallizes in the [[monoclinic crystal system]] ([[Pearson symbol]] mS60, [[space group]] C2/c No. 15, lattice constants ''a'' = 1247 pm, ''b'' = 1058 pm, ''c'' = 817 pm) and is [[isotypic]] with [[uranium tetrafluoride]] or [[zirconium(IV) fluoride]].<ref name=e48>Peterson, p. 48</ref><ref name="BKF_3_4"/><ref name=f1>{{cite journal|last1=Keenan|first1=Thomas K.|last2=Asprey|first2=Larned B.|title=Lattice constants of actinide tetrafluorides including berkelium|journal=Inorganic Chemistry|volume=8|pages=235|year=1969|doi=10.1021/ic50072a011}}</ref>
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| Berkelium(III) fluoride (BkF<sub>3</sub>) is also a yellow-green solid, but it has two crystalline structures. The most stable phase at low temperatures has an [[Orthorhombic crystal system|orthorhombic]] symmetry, isotypic with [[yttrium(III) fluoride]] (Pearson symbol oP16, space group Pnma, No. 62, ''a'' = 670 pm, ''b'' = 709 pm, ''c'' = 441 pm). Upon heating to 350 to 600 °C, it transforms to a [[trigonal crystal system|trigonal]] structure found in [[lanthanum(III) fluoride]] (Pearson symbol hP24, space group P{{overline|3}}c1, No. 165, ''a'' = 697 pm, ''c'' = 714 pm).<ref name=e48/><ref name="BKF_3_4">{{cite journal|last1=Ensor|first1=D|title=Absorption spectrophotometric study of berkelium(III) and (IV) fluorides in the solid state|journal=Journal of Inorganic and Nuclear Chemistry|volume=43|pages=1001|year=1981|doi=10.1016/0022-1902(81)80164-9}}</ref><ref>{{cite journal|last1=Peterson|first1=J.R.|last2=Cunningham|first2=B.B.|title=Crystal structures and lattice parameters of the compounds of berkelium—IV berkelium trifluoride☆|journal=Journal of Inorganic and Nuclear Chemistry|volume=30|pages=1775|year=1968|doi=10.1016/0022-1902(68)80353-7}}</ref>
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| Visible amounts of [[berkelium(III) chloride]] (BkCl<sub>3</sub>) were first isolated and characterized in 1962, and weighed only 3 billionths of a [[gram]]. It can be prepared by introducing [[hydrogen chloride]] vapors into an evacuated quartz tube containing berkelium oxide at a temperature of about 500 °C.<ref name=o1/> This green solid has a melting point of 603 °C<ref name="HOWI_1969"/> and crystallizes in the [[hexagonal crystal system]] isotypic with [[uranium(III) chloride]] (Pearson symbol hP8, space group P6<sub>3</sub>/m, No. 176).<ref>{{cite journal|last1=Peterson|first1=J.R.|last2=Cunningham|first2=B.B.|title=Crystal structures and lattice parameters of the compounds of berkelium—IIBerkelium trichloride|journal=Journal of Inorganic and Nuclear Chemistry|volume=30|pages=823|year=1968|doi=10.1016/0022-1902(68)80443-9}}</ref><ref>{{cite journal|last1=Peterson|first1=J. R.|last2=Young|first2=J. P.|last3=Ensor|first3=D. D.|last4=Haire|first4=R. G.|title=Absorption spectrophotometric and x-ray diffraction studies of the trichlorides of berkelium-249 and californium-249|journal=Inorganic Chemistry|volume=25|pages=3779|year=1986|doi=10.1021/ic00241a015}}</ref> Upon heating to just below its melting point, BkCl<sub>3</sub> converts into an [[orthorhombic crystal system|orthorhombic]] phase.<ref name=e52>Peterson, p. 52</ref> The hexahydrate BkCl<sub>3</sub>·6H<sub>2</sub>O ([[berkelium trichloride hexahydrate]]) has a [[monoclinic crystal system|monoclinic]] structure with the lattice constants ''a'' = 966 pm, ''b'' = 654 pm and ''c'' = 797 pm.<ref name=e48/><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|pages=147|year=1971|doi=10.1021/ic50095a029}}</ref> Another berkelium(III) chloride, Cs<sub>2</sub>NaBkCl<sub>6</sub> can be crystallized from a chilled aqueous solution containing berkelium(III) hydroxide, hydrochloric acid and [[caesium chloride]]. It has a [[face-centered cubic]] structure where Bk(III) ions are surrounded by chloride ions in an octahedral configuration.<ref name=e52/>
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| The ternary berkelium(IV) chloride Cs<sub>2</sub>BkCl<sub>6</sub> is obtained by dissolving berkelium(IV) hydroxide in a chilled solution of [[caesium chloride]] in concentrated [[hydrochloric acid]]. It forms orange hexagonal crystals with the lattice constants ''a'' = 745.1 pm and ''c'' = 1209.7 pm. The average radius of the BkCl<sub>6</sub><sup>2–</sup> ion in this compound is estimated as 270 pm.<ref name=e51/>
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| Two forms of berkelium(III) bromide are known, a monoclinic with berkelium coordination 6 and orthorhombic with coordination 8;<ref name=e38>Peterson, p. 38</ref> the latter is less stable and transforms to the former phase upon heating to about 350 °C. An important phenomenon for radioactive solids has been studied for these two crystal forms: the structures of fresh and aged <sup>249</sup>BkBr<sub>3</sub> samples were studied using [[X-ray diffraction]] over a period longer than 3 years, so that various fractions of <sup>249</sup>Bk had [[beta decay]]ed to <sup>249</sup>[[californium|Cf]]. No change in structure was observed upon the <sup>249</sup>BkBr<sub>3</sub>—<sup>249</sup>CfBr<sub>3</sub> transformation, even though the orthorhombic bromide was previously unknown for californium. However, other differences were noted for <sup>249</sup>BkBr<sub>3</sub> and <sup>249</sup>CfBr<sub>3</sub>. For example, the latter could be reduced with hydrogen to<sup>249</sup>CfBr<sub>2</sub>, but the former could be not – this result was reproduced on individual <sup>249</sup>BkBr<sub>3</sub> and<sup>249</sup>CfBr<sub>3</sub> samples, as well on the samples containing both bromides.<ref name=conv/> The intergrowth of californium in berkelium occurs at a rate of 0.22% per day and is an intrinsic obstacle in studying berkelium properties. Besides a chemical contamination, <sup>249</sup>Cf, as an [[alpha emitter]] brings undesirable self-damage of the crystal lattice due to the resulting self-heating. This can be avoided by performing measurements as a function of time and extrapolating the obtained results.<ref name=e47/>
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| Berkelium(III) iodide forms hexagonal crystals with the lattice constants ''a'' = 758.4 pm and ''c'' = 2087 pm.<ref name=e48/> The known [[oxyhalide]]s of berkelium include BkOCl, BkOBr and BkOI; they all crystallize in a [[tetragonal]] lattice.<ref name=e53/>
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| ==Other inorganic compounds==
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| ===Pnictides===
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| The mono[[pnictide]]s of berkelium-249 are known for the elements [[nitrogen]],<ref name=n1>{{cite journal|last1=Stevenson|first1=J|last2=Peterson|first2=J|title=Preparation and structural studies of elemental curium-248 and the nitrides of curium-248 and berkelium-249|journal=Journal of the Less Common Metals|volume=66|pages=201|year=1979|doi=10.1016/0022-5088(79)90229-7}}</ref><ref name="pnictides"/> [[phosphorus]],<ref name="pnictides"/> [[arsenic]]<ref name="pnictides"/> and [[antimony]].<ref name="pnictides"/> They are prepared by the reaction of either berkelium(III) hydride (BkH<sub>3</sub>) or metallic berkelium with these elements at elevated temperatures (about 600 °C) under high vacuum in quartz ampoules. They crystallize in the [[cubic crystal system]] with the lattice constant of 495.1 pm for BkN, 566.9 pm for BkP, 582.9 for BkAs and 619.1 pm for BkSb.<ref name="pnictides">{{cite journal|last1=Damien|first1=D.|last2=Haire|first2=R.G.|last3=Peterson|first3=J.R.|title=Preparation and lattice parameters of <sup>249</sup>Bk monopnictides|journal=Journal of Inorganic and Nuclear Chemistry|volume=42|pages=995|year=1980|doi=10.1016/0022-1902(80)80390-3}}</ref> These lattice constant values are smaller than those in curium pnictides, but are comparable to those of terbium pnictides.<ref name=e53/>
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| ===Chalcogenides===
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| Berkelium(III) sulfide, Bk<sub>2</sub>S<sub>3</sub>, has been prepared by either treating berkelium oxide with a mixture of [[hydrogen sulfide]] and [[carbon disulfide]]vapors at 1130 °C, or by directly reacting metallic berkelium with sulfur. These procedures yield brownish-black crystals with a cubic symmetry and lattice constant ''a'' = 844 pm.<ref name=e53/>
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| ===Other compounds===
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| Berkelium(III) and berkelium(IV) hydroxides are both stable in 1 [[Molar concentration|M]] [[sodium hydroxide]] solutions. Berkelium(III) [[phosphate]] (BkPO<sub>4</sub>) has been prepared as a solid, which shows strong fluorescence under [[Ion laser|argon laser]] (514.5 nm line) excitation.<ref>Peterson, pp. 39–40</ref> Berkelium hydrides are produced by reacting metal with hydrogen gas at temperatures about 250 °C.<ref name=n1/> They are non-stoichiometric with the nominal formula BkH<sub>2+x</sub> (0 < x < 1). Whereas the trihydride has a hexagonal symmetry, the dihydride crystallizes in an ''fcc'' structure with the lattice constant ''a'' = 523 pm.<ref name=e53>Peterson, p. 53</ref> Several other salts of berkelium are known, including Bk<sub>2</sub>O<sub>2</sub>S, (BkNO<sub>3</sub>)<sub>3</sub>·4H<sub>2</sub>O, BkCl<sub>3</sub>·6H<sub>2</sub>O, Bk<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·12H<sub>2</sub>O and Bk<sub>2</sub>(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>·4H<sub>2</sub>O.<ref name=e47/> Thermal decomposition at about 600 °C in an argon atmosphere (to avoid oxidation to Bk<sub>2</sub>O) of Bk<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·12H<sub>2</sub>O yields the body-centered orthorhombic crystals of berkelium(IV) oxysulfate (Bk<sub>2</sub>O<sub>2</sub>SO<sub>4</sub>). This compound is thermally stable to at least 1000 °C in an inert atmosphere.<ref name=e54>Peterson, p. 54</ref>
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| ==Organoberkelium compounds==
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| Berkelium forms a trigonal (η<sup>5</sup>–C<sub>5</sub>H<sub>5</sub>)<sub>3</sub>Bk complex with three [[Cyclopentadienyl complex|cyclopentadienyl]] rings, which can be synthesized by reacting berkelium(III) chloride with the molten beryllocene Be(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> at about 70 °C. It has an amber color and orthorhombic symmetry, with the lattice constants of ''a'' = 1411 pm, ''b'' = 1755 pm and ''c'' = 963 pm and the calculated density of 2.47 g/cm<sup>3</sup>. The complex is stable to heating to at least 250 °C, and sublimates without melting at about 350 °C. The high radioactivity of berkelium gradually destroys the compound within a period of weeks.<ref name=o1>{{cite journal|last1=Laubereau|first1=Peter G.|last2=Burns|first2=John H.|title=Microchemical preparation of tricyclopentadienyl compounds of berkelium, californium, and some lanthanide elements|journal=Inorganic Chemistry|volume=9|pages=1091|year=1970|doi=10.1021/ic50087a018}}</ref><ref>Christoph Elschenbroich ''Organometallic Chemistry'', 6th Edition, Wiesbaden 2008, ISBN 978-3-8351-0167-8, pp. 583–584</ref> One C<sub>5</sub>H<sub>5</sub> ring in (η<sup>5</sup>–C<sub>5</sub>H<sub>5</sub>)<sub>3</sub>Bk can be substituted by chlorine to yield [Bk(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub>Cl]<sub>2</sub>. The optical absorption spectra of this compound are very similar to those of (η<sup>5</sup>–C<sub>5</sub>H<sub>5</sub>)<sub>3</sub>Bk.<ref name=e54/><ref name=e41>Peterson, p. 41</ref>
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| ==See also==
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| *[[Berkelium]]
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| *[[Compounds of californium]]
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| ==References==
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| {{reflist|2}}
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| ==Bibliography==
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| {{Commons|Berkelium}}
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| {{Wikipedia books|Berkelium}}
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| * {{Greenwood&Earnshaw2nd}}
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| * Holleman, Arnold F. and Wiberg, Nils ''Textbook of Inorganic Chemistry'', 102 Edition, de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1.
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| * Peterson J. R. and Hobart D. E. [http://books.google.com/books?id=U-YOlLVuV1YC&pg=PA29 "The Chemistry of Berkelium"] in [[Harry Julius Emeléus]] (Ed.) ''Advances in inorganic chemistry and radiochemistry'', Volume 28, Academic Press, 1984 ISBN 0-12-023628-1, pp. 29–64, {{doi|10.1016/S0898-8838(08)60204-4}}
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| [[Category:Actinides]]
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| [[Category:Berkelium]]
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Fredrick is how I'm known as and I believe it sounds fairly good when you say it. The occupation I've been occupying for many years is a supervisor but quickly I'll be on my personal. What me and my family members love is bee keeping and I would by no means give it up. Wyoming is where I've usually been living and I don't plan on changing it. See what's new on my website here: http://isabeldeloitte.pen.io/
My web site: Delhi University