Difference between revisions of "Berkelium" - New World Encyclopedia

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:'''''Bk''' redirects here. For other uses of the abbreviation, see [[BK]].''
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{{Elementbox_header | number=97 | symbol=Bk | name=berkelium | left=[[curium]] | right=[[californium]] | above=[[terbium|Tb]] | below=(Uqs) | color1=#ff99cc | color2=black }}
 
{{Elementbox_header | number=97 | symbol=Bk | name=berkelium | left=[[curium]] | right=[[californium]] | above=[[terbium|Tb]] | below=(Uqs) | color1=#ff99cc | color2=black }}
 
{{Elementbox_series | [[actinide]]s }}
 
{{Elementbox_series | [[actinide]]s }}
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{{Elementbox_cas_number | 7440-40-6 }}
 
{{Elementbox_cas_number | 7440-40-6 }}
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{{Elementbox_isotopes_begin | isotopesof=berkelium | color1=#ff99cc | color2=black }}
 
{{Elementbox_isotopes_decay2 | mn=245 | sym=Bk
 
{{Elementbox_isotopes_decay2 | mn=245 | sym=Bk
 
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{{Elementbox_footer | color1=#ff99cc | color2=black }}
 
{{Elementbox_footer | color1=#ff99cc | color2=black }}
  
'''Berkelium''' ([[International Phonetic Alphabet|IPA]]: {{IPA|/bəˈkiːliəm/}}) is a [[synthetic element]] in the [[periodic table]] that has the symbol '''Bk''' and [[atomic number]] 97. A [[radioactive]] [[metal]]lic element in the [[actinide]] series, berkelium was first synthesized by bombarding [[americium]] with [[alpha particle]]s ([[helium]] [[ion]]s) and was named after [[Berkeley, California]] and the [[University of California, Berkeley]]. Berkelium was the fifth [[transuranic element]] to be synthesized.
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'''Berkelium''' (chemical symbol '''Bk''', [[atomic number]] 97) is a [[synthetic element]] in the [[periodic table]]. A [[radioactive]] [[metal]]lic element in the [[actinide]] series, it was first synthesized by bombarding [[americium]] with [[alpha particle]]s ([[helium]] [[ion]]s) and was named after [[Berkeley, California]] and the [[University of California, Berkeley]]. Berkelium was the fifth [[transuranic element]] to be synthesized. Currently, the main interest in this element lies in basic research, and practical applications have not been devised.
 +
 
 +
==History ==
 +
 
 +
Berkelium was [[discovery of the chemical elements|first synthesized]] by [[Glenn T. Seaborg]], [[Albert Ghiorso]], Stanley G. Thompson, and Kenneth Street, Jr., at the [[University of California, Berkeley]] in December 1949. The team used a [[cyclotron]] to bombard a [[milligram]]-sized target of <sup>241</sup>[[americium|Am]] with [[alpha particle]]s to produce <sup>243</sup>Bk ([[half-life]] 4.5 hours) and two [[free neutron]]s. One of the longest lived [[isotope]]s of the element, <sup>249</sup>Bk (half-life 330 days), was later synthesized by subjecting a <sup>244</sup>[[curium|Cm]] target with an intense beam of [[neutron]]s.
  
 
== Notable characteristics ==
 
== Notable characteristics ==
Weighable amounts of <sup>249</sup>Bk (half-life 314 days) make it possible to determine some of its properties using macroscopic quantities.  [[As of 2004]] it had not been isolated in its elemental form, but it is predicted to be a silvery metal that would easily [[oxidation|oxidize]] in air at elevated temperatures and would be [[solubility|soluble]] in dilute [[mineral acid]]s.
 
  
[[X-ray diffraction]] techniques have been used to identify various berkelium [[compound (chemistry)|compound]]s such as  berkelium dioxide (BkO<sub>2</sub>), berkelium fluoride (BkF<sub>3</sub>), berkelium oxychloride (BkOCl), and berkelium trioxide (BkO<sub>3</sub>). In [[1962]] visible amounts of berkelium [[chloride]] (BkCl<sub>3</sub>) were isolated that weighed 3 billionths of a [[gram]]. This was the first time visible amounts of a pure berkelium compound were produced.
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Berkelium is an [[inner transition metal]] (or actinide) that lies in period 7 of the [[periodic table]], between [[curium]] and [[californium]]. Weighable amounts of <sup>249</sup>Bk (half-life 314 days) make it possible to determine some of its properties using macroscopic quantities. As of 2004, it had not been isolated in its elemental form, but it is predicted to be a silvery metal that would easily [[oxidation|oxidize]] in air at elevated temperatures and would be [[solubility|soluble]] in dilute [[mineral acid]]s.
 +
 
 +
=== Isotopes ===
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Many [[radioisotope]]s of berkelium have been characterized, with the most stable being <sup>247</sup>Bk with a [[half-life]] of 1380 years, <sup>248</sup>Bk with a half-life of >9 years, and <sup>249</sup>Bk with a half-life of 330 days. All of the remaining [[radioactive]] isotopes have half-lives that are less than 5 days, and the majority of these have half-lives that are less than 5 hours. This element also has 2 [[meta state]]s, with the most stable being <sup>248m</sup>Bk (t<sub>½</sub> 23.7 hours). The isotopes of berkelium range in [[atomic weight]] from 235.057 [[atomic mass unit|amu]] (<sup>235</sup>Bk) to 254.091 amu (<sup>254</sup>Bk).
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== Compounds ==
  
Like other actinides, berkelium [[bio-accumulate]]s in [[skeleton|skeletal]] tissue.{{Fact|date=February 2007}} This element has no known uses outside of basic research and plays no biological role.
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[[X-ray diffraction]] techniques have been used to identify various berkelium [[compound (chemistry)|compound]]s such as  berkelium dioxide (BkO<sub>2</sub>), berkelium fluoride (BkF<sub>3</sub>), berkelium oxychloride (BkOCl), and berkelium trioxide (BkO<sub>3</sub>). In 1962, visible amounts of berkelium [[chloride]] (BkCl<sub>3</sub>) were isolated that weighed 3 billionths of a [[gram]]. This was the first time visible amounts of a pure berkelium compound were produced.
  
==History ==
+
== Biological role ==
Berkelium was [[discovery of the chemical elements|first synthesized]] by [[Glenn T. Seaborg]], [[Albert Ghiorso]], Stanley G. Thompson, and Kenneth Street, Jr at the [[University of California, Berkeley]] in December [[1949]]. The team used a [[cyclotron]] to bombard a [[milligram]]-sized target of <sup>241</sup>[[americium|Am]] with [[alpha particle]]s to produce <sup>243</sup>Bk ([[half-life]] 4.5 hours) and two [[free neutron]]s. One of the longest lived [[isotope]]s of the element, <sup>249</sup>Bk (half-life 330 days), was later synthesized by subjecting a <sup>244</sup>[[curium|Cm]] target with an intense beam of [[neutron]]s.
 
  
== Isotopes ==
+
Berkelium plays no biological role. Yet, like other actinides, it is thought to be capable of [[bioaccumulation]] in [[skeleton|skeletal]] tissue.
19 [[radioisotope]]s of berkelium have been characterized, with the most stable being <sup>247</sup>Bk with a [[half-life]] of 1380 years, <sup>248</sup>Bk with a half-life of >9 years, and <sup>249</sup>Bk with a half-life of 330 days.  All of the remaining [[radioactive]] isotopes have half-lives that are less than 5 days, and the majority of these have half-lives that are less than 5 hours. This element also has 2 [[meta state]]s, with the most stable being <sup>248m</sup>Bk (t<sub>½</sub> 23.7 hours). The isotopes of berkelium range in [[atomic weight]] from 235.057 [[atomic mass unit|amu]] (<sup>235</sup>Bk) to 254.091 amu (<sup>254</sup>Bk).
 
  
 
==References==
 
==References==
*[http://periodic.lanl.gov/elements/97.html Los Alamos National Laboratory - Berkelium]
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*[http://education.jlab.org/itselemental/ele097.html It's Elemental - Berkelium]
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* Emsley, John. 2001. ''Nature's Building Blocks: An A&ndash;Z Guide to the Elements''. Oxford: Oxford Univ. Press. ISBN 0198503407 and ISBN 978-0198503408.
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* Greenwood, N.N., and A. Earnshaw. 1998. ''Chemistry of the Elements'' 2nd ed. Oxford, UK; Burlington, MA: Butterworth-Heinemann. ISBN 0750633654. [http://www.knovel.com/knovel2/Toc.jsp?BookID=402&VerticalID=0 Online version].
 +
 
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* Hampel, Clifford A. 1968. ''The Encyclopedia of the Chemical Elements''. New York: Reinhold Book Corp. ISBN 0442155980 and ISBN 978-0442155988.
 +
 
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* Morss, Lester R., Norman M. Edelstein, and Jean Fuger, eds. 2006. ''The Chemistry of the Actinide and Transactinide Elements''. 3rd ed. 5 vols. Joseph J. Katz, adapter. Dordrecht: Springer. ISBN 1402035551 and ISBN 978-1402035555.
 +
 
 +
* Stwertka, Albert. 1998. ''Guide to the Elements''. Rev. ed. Oxford: Oxford University Press. ISBN 0-19-508083-1.
 +
 
 +
* [http://periodic.lanl.gov/elements/97.html "Berkelium"] Los Alamos National Laboratory, Chemistry Division. Retrieved March 14, 2007.
  
 
== External links ==
 
== External links ==
{{Commons|Berkelium}}
 
*[http://www.webelements.com/webelements/elements/text/Bk/index.html WebElements.com - Berkelium]
 
  
 +
*[http://www.webelements.com/webelements/elements/text/Bk/index.html "Berkelium"] WebElements.com. Retrieved March 14, 2007.
 +
*[http://education.jlab.org/itselemental/ele097.html "Berkelium"] It's Elemental. Retrieved March 14, 2007.
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[[Category:Physical sciences]]
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[[Category:Chemistry]]
 
[[Category:Chemical elements]]
 
[[Category:Chemical elements]]
[[Category:Actinides]]
 
[[Category:University of California, Berkeley]]
 
 
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Revision as of 22:35, 14 March 2007

97 curiumberkeliumcalifornium
Tb

Bk

(Uqs)
Bk-TableImage.png
periodic table
General
Name, Symbol, Number berkelium, Bk, 97
Chemical series actinides
Group, Period, Block n/a, 7, f
Appearance unknown, probably silvery
white or metallic gray
Atomic mass (247) g/mol
Electron configuration [Rn] 5f9 7s2
Electrons per shell 2, 8, 18, 32, 27, 8, 2
Physical properties
Phase solid
Density (near r.t.) (alpha) 14.78 g/cm³
Density (near r.t.) (beta) 13.25 g/cm³
Melting point (beta) 1259 K
(986 °C, 1807 °F)
Atomic properties
Oxidation states 3, 4
Electronegativity 1.3 (Pauling scale)
Ionization energies 1st: 601 kJ/mol
Miscellaneous
Crystal structure hexagonal close-packed
Magnetic ordering no data
Thermal conductivity (300 K) 10 W/(m·K)
CAS registry number 7440-40-6
Notable isotopes
Main article: Isotopes of berkelium
iso NA half-life DM DE (MeV) DP
245Bk syn 4.94 d ε 0.810 245Cm
α 6.455 241Am
246Bk syn 1.8 d α 6.070 242Am
ε 1.350 246Cm
247Bk syn 1380 y α 5.889 243Am
248Bk syn >9 y α 5.803 244Am
249Bk syn 330 d α 5.526 245Am
SF - -
β- 0.125 249Cf

Berkelium (chemical symbol Bk, atomic number 97) is a synthetic element in the periodic table. A radioactive metallic element in the actinide series, it was first synthesized by bombarding americium with alpha particles (helium ions) and was named after Berkeley, California and the University of California, Berkeley. Berkelium was the fifth transuranic element to be synthesized. Currently, the main interest in this element lies in basic research, and practical applications have not been devised.

History

Berkelium was first synthesized by Glenn T. Seaborg, Albert Ghiorso, Stanley G. Thompson, and Kenneth Street, Jr., at the University of California, Berkeley in December 1949. The team used a cyclotron to bombard a milligram-sized target of 241Am with alpha particles to produce 243Bk (half-life 4.5 hours) and two free neutrons. One of the longest lived isotopes of the element, 249Bk (half-life 330 days), was later synthesized by subjecting a 244Cm target with an intense beam of neutrons.

Notable characteristics

Berkelium is an inner transition metal (or actinide) that lies in period 7 of the periodic table, between curium and californium. Weighable amounts of 249Bk (half-life 314 days) make it possible to determine some of its properties using macroscopic quantities. As of 2004, it had not been isolated in its elemental form, but it is predicted to be a silvery metal that would easily oxidize in air at elevated temperatures and would be soluble in dilute mineral acids.

Isotopes

Many radioisotopes of berkelium have been characterized, with the most stable being 247Bk with a half-life of 1380 years, 248Bk with a half-life of >9 years, and 249Bk with a half-life of 330 days. All of the remaining radioactive isotopes have half-lives that are less than 5 days, and the majority of these have half-lives that are less than 5 hours. This element also has 2 meta states, with the most stable being 248mBk (t½ 23.7 hours). The isotopes of berkelium range in atomic weight from 235.057 amu (235Bk) to 254.091 amu (254Bk).

Compounds

X-ray diffraction techniques have been used to identify various berkelium compounds such as berkelium dioxide (BkO2), berkelium fluoride (BkF3), berkelium oxychloride (BkOCl), and berkelium trioxide (BkO3). In 1962, visible amounts of berkelium chloride (BkCl3) were isolated that weighed 3 billionths of a gram. This was the first time visible amounts of a pure berkelium compound were produced.

Biological role

Berkelium plays no biological role. Yet, like other actinides, it is thought to be capable of bioaccumulation in skeletal tissue.

References
ISBN links support NWE through referral fees

  • Greenwood, N.N., and A. Earnshaw. 1998. Chemistry of the Elements 2nd ed. Oxford, UK; Burlington, MA: Butterworth-Heinemann. ISBN 0750633654. Online version.
  • Morss, Lester R., Norman M. Edelstein, and Jean Fuger, eds. 2006. The Chemistry of the Actinide and Transactinide Elements. 3rd ed. 5 vols. Joseph J. Katz, adapter. Dordrecht: Springer. ISBN 1402035551 and ISBN 978-1402035555.
  • Stwertka, Albert. 1998. Guide to the Elements. Rev. ed. Oxford: Oxford University Press. ISBN 0-19-508083-1.
  • "Berkelium" Los Alamos National Laboratory, Chemistry Division. Retrieved March 14, 2007.

External links

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