Difference between revisions of "Mendelevium" - New World Encyclopedia
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| − | '''Mendelevium''' (chemical symbol '''Md''' (formerly '''Mv'''), [[atomic number]] 101), also known as '''unnilunium''' (symbol '''Unu'''), is a [[synthetic element]] in the [[periodic table]]. A [[metal]]lic [[radioactive]] [[transuranic]] element of the [[actinide]] | + | '''Mendelevium''' (chemical symbol '''Md''' (formerly '''Mv'''), [[atomic number]] 101), also known as '''unnilunium''' (symbol '''Unu'''), is a [[synthetic element]] in the [[periodic table]]. A [[metal]]lic [[radioactive]] [[transuranic element]]<ref>"Transuranic elements" are the [[chemical element]]s with [[atomic number]]s greater than that of [[uranium]] (atomic number 92).</ref> of the [[actinide]] series, mendelevium is synthesized by bombarding [[einsteinium]] with [[alpha particle]]s. |
== History == | == History == | ||
| − | Mendelevium was named after [[Dmitri Mendeleev]] (surname also spelt as Mendeleyev, Mendeléef, or even Mendelejeff; first name sometimes spelt as Dmitry or Dmitriy). It was first [[discovery of the chemical elements|synthesized]] by [[Albert Ghiorso]] (team leader), [[Glenn T. Seaborg]], [[Bernard Harvey]],[[Greg Choppin]], and [[Stanley G. Thompson]] in early | + | Mendelevium was named after [[Dmitri Mendeleev]] (surname also spelt as Mendeleyev, Mendeléef, or even Mendelejeff; first name sometimes spelt as Dmitry or Dmitriy). It was first [[discovery of the chemical elements|synthesized]] by [[Albert Ghiorso]] (team leader), [[Glenn T. Seaborg]], [[Bernard Harvey]],[[Greg Choppin]], and [[Stanley G. Thompson]] in early 1955 at the University of California, Berkeley. The team produced <sup>256</sup>Md ([[half-life]] of 76 minutes) when they bombarded an <sup>253</sup>[[einsteinium|Es]] target with [[alpha particle]]s ([[helium]] nuclei) in the [[Berkeley Radiation Laboratory]]'s 60-inch [[cyclotron]] (<sup>256</sup>Md was the first element to be synthesized one-atom-at-a-time). Element 101 was the ninth [[transuranic element]] synthesized. |
== Notable characteristics == | == Notable characteristics == | ||
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=== Isotopes === | === Isotopes === | ||
| − | 15 [[radioisotope]]s of mendelevium have been characterized, with the most stable being <sup>258</sup>Md with a [[half-life]] of 51.5 days, <sup>260</sup>Md with a half-life of 31.8 days, and <sup>257</sup>Md with a half-life of 5.52 hours. | + | 15 [[radioisotope]]s of mendelevium have been characterized, with the most stable being <sup>258</sup>Md with a [[half-life]] of 51.5 days, <sup>260</sup>Md with a half-life of 31.8 days, and <sup>257</sup>Md with a half-life of 5.52 hours. All of the remaining [[radioactive]] isotopes have half-lives that are less than 97 minutes, and the majority of these have half-lives that are less than 5 minutes. This element also has 1 [[meta state]], <sup>258m</sup>Md (t<sub>½</sub> 57 minutes). The isotopes of mendelevium range in [[atomic weight]] from 245.091 [[atomic mass unit|amu]] (<sup>245</sup>Md) to 260.104 amu (<sup>260</sup>Md). |
== See also == | == See also == | ||
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* [[Periodic table]] | * [[Periodic table]] | ||
* [[Radioactive decay]] | * [[Radioactive decay]] | ||
| + | |||
| + | == Notes == | ||
| + | <references/> | ||
==References== | ==References== | ||
Revision as of 16:19, 21 March 2007
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| General | ||||||||||||||||||||||||||||||||||||||||
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| Name, Symbol, Number | mendelevium, Md, 101 | |||||||||||||||||||||||||||||||||||||||
| Chemical series | actinides | |||||||||||||||||||||||||||||||||||||||
| Group, Period, Block | n/a, 7, f | |||||||||||||||||||||||||||||||||||||||
| Appearance | unknown, probably silvery white or metallic gray | |||||||||||||||||||||||||||||||||||||||
| Atomic mass | (258) g/mol | |||||||||||||||||||||||||||||||||||||||
| Electron configuration | [Rn] 5f13 7s2 | |||||||||||||||||||||||||||||||||||||||
| Electrons per shell | 2, 8, 18, 32, 31, 8, 2 | |||||||||||||||||||||||||||||||||||||||
| Physical properties | ||||||||||||||||||||||||||||||||||||||||
| Phase | solid | |||||||||||||||||||||||||||||||||||||||
| Melting point | 1100 K (827 °C, 1521 °F) | |||||||||||||||||||||||||||||||||||||||
| Atomic properties | ||||||||||||||||||||||||||||||||||||||||
| Oxidation states | 2, 3 | |||||||||||||||||||||||||||||||||||||||
| Electronegativity | 1.3 (Pauling scale) | |||||||||||||||||||||||||||||||||||||||
| Ionization energies | 1st: 635 kJ/mol | |||||||||||||||||||||||||||||||||||||||
| Miscellaneous | ||||||||||||||||||||||||||||||||||||||||
| Magnetic ordering | no data | |||||||||||||||||||||||||||||||||||||||
| CAS registry number | 7440-11-1 | |||||||||||||||||||||||||||||||||||||||
| Notable isotopes | ||||||||||||||||||||||||||||||||||||||||
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Mendelevium (chemical symbol Md (formerly Mv), atomic number 101), also known as unnilunium (symbol Unu), is a synthetic element in the periodic table. A metallic radioactive transuranic element[1] of the actinide series, mendelevium is synthesized by bombarding einsteinium with alpha particles.
History
Mendelevium was named after Dmitri Mendeleev (surname also spelt as Mendeleyev, Mendeléef, or even Mendelejeff; first name sometimes spelt as Dmitry or Dmitriy). It was first synthesized by Albert Ghiorso (team leader), Glenn T. Seaborg, Bernard Harvey,Greg Choppin, and Stanley G. Thompson in early 1955 at the University of California, Berkeley. The team produced 256Md (half-life of 76 minutes) when they bombarded an 253Es target with alpha particles (helium nuclei) in the Berkeley Radiation Laboratory's 60-inch cyclotron (256Md was the first element to be synthesized one-atom-at-a-time). Element 101 was the ninth transuranic element synthesized.
Notable characteristics
Mendelevium is an inner transition metal (or actinide) that lies in period 7 of the periodic table, between fermium and nobelium. Researchers have shown that mendelevium has a moderately stable dipositive (II) oxidation state in addition to the more characteristic (for actinide elements) tripositive (III) oxidation state. 256Md has been used to find out some of the chemical properties of this element while in an aqueous solution. There are no other uses of mendelevium and only trace amounts of the element have ever been produced.
Isotopes
15 radioisotopes of mendelevium have been characterized, with the most stable being 258Md with a half-life of 51.5 days, 260Md with a half-life of 31.8 days, and 257Md with a half-life of 5.52 hours. All of the remaining radioactive isotopes have half-lives that are less than 97 minutes, and the majority of these have half-lives that are less than 5 minutes. This element also has 1 meta state, 258mMd (t½ 57 minutes). The isotopes of mendelevium range in atomic weight from 245.091 amu (245Md) to 260.104 amu (260Md).
See also
Notes
- ↑ "Transuranic elements" are the chemical elements with atomic numbers greater than that of uranium (atomic number 92).
ReferencesISBN links support NWE through referral fees
- Emsley, John. 2001. Nature's Building Blocks: An A–Z Guide to the Elements. Oxford: Oxford Univ. Press. ISBN 0198503407 and ISBN 978-0198503408.
- Greenwood, N.N., and A. Earnshaw. 1998. Chemistry of the Elements 2nd ed. Oxford, UK; Burlington, MA: Butterworth-Heinemann. ISBN 0750633654. Online version.
- Hampel, Clifford A. 1968. The Encyclopedia of the Chemical Elements. New York: Reinhold Book Corp. ISBN 0442155980 and ISBN 978-0442155988.
- 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.
- "Mendelevium" Los Alamos National Laboratory, Chemistry Division. Retrieved March 16, 2007.
External links
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