From Wikipedia, the free encyclopedia
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|
| General |
| Name, Symbol, Number |
mendelevium, Md, 101 |
| Element category |
actinides |
| Group, Period, Block |
n/a, 7, f |
| Appearance |
unknown, probably silvery
white or metallic gray |
| Standard atomic weight |
(258) g·mol−1 |
| 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 |
| Most-stable isotopes |
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| References |
Mendelevium (pronounced /ˌmɛndəˈlɛviəm/ or /ˌmɛndəˈliːviəm/) is a synthetic element with the symbol Md (formerly Mv) and the atomic number 101. A metallic radioactive transuranic element of the actinides, mendelevium is synthesized by bombarding einsteinium with alpha particles and was named after Dmitri Mendeleev, who was responsible for the Periodic Table.
[edit] Characteristics
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, the latter being the more dominantly exhibited state in an aqueous solution (Chromatography being the process used). Sometimes, Mendelevium can even be shown to exhibit a monopositive (I) state. [1] 256Md has been used to find out some of the chemical properties of this element while in an aqueous solution. There are no other known uses of mendelevium and only trace amounts of the element have ever been produced. Other isotopes of Mendelevium, all radioactive have been discovered, with 258Md being the most stable with a two-month half-life (about 55 days). [2] Other isotopes range from 248 to 258 mass numbers and half-lives from a few seconds to about 55 days. The original 256Md had a half-life of 76 minutes. [3] It is assumed that Mendelevium's standard state is solid at 298K and its classification is metallic. [4]
[edit] History
Mendelevium (for Dmitri Mendeleev, surname commonly transliterated into Latin script as Mendeleev, Mendeleyev, Mendeléef, or even Mendelejeff, and first name sometimes transliterated as Dmitry or Dmitriy) was first synthesized by Albert Ghiorso (team leader), Glenn T. Seaborg, Gregory R. Choppin, Bernard G. Harvey, 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. The first 17 atoms of this element were created and analyzed using the ion-exchange adsorption-elution method. During the process, Mendelevium behaved very much like Thulium, its naturally-occurring homologue. [5]
[edit] 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 u (245Md) to 260.104 u (260Md).
[edit] References
[edit] External links
