Mendelevium

101 fermium ← mendelevium → nobelium Tm ↑ Md ↓ (Upu) periodic table
General
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
Main article: Isotopes of mendelevium iso NA half-life DM DE (MeV) DP 257Md syn 5.52 h ε 0.406 257Fm α 7.558 253Es SF - - 258Md syn 51.5 d ε 1.230 258Fm 260Md syn 31.8 d SF - - α 7.000 256Es ε - 260Fm β- 1.000 260No

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 of the actinide series, mendelevium is synthesized by bombarding einsteinium with alpha particles. Only trace amounts of the element have been produced. The element is of interest mainly for research purposes, and practical applications have yet to be developed.

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 of the actinide series, situated in period seven 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. Currently, there are no practical uses of mendelevium, and only trace amounts of the element have 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 five minutes. This element also has one meta state, ^258mMd (t_½ 57 minutes). The isotopes of mendelevium range in atomic weight from 245.091 amu (²⁴⁵Md) to 260.104 amu (²⁶⁰Md).

See also

• Chemical element
• Inner transition metal
• Metal
• Periodic table
• Radioactive decay

References

ISBN links support NWE through referral fees

• Emsley, John. Nature's Building Blocks: An A–Z Guide to the Elements. Oxford: Oxford Univ. Press, 2001. ISBN 0198503407

• Greenwood, N.N., and A. Earnshaw. Chemistry of the Elements 2nd ed. Oxford, UK; Burlington, MA: Butterworth-Heinemann, 1998. ISBN 0750633654

• Hampel, Clifford A. The Encyclopedia of the Chemical Elements. New York: Reinhold Book Corp, 1968. ISBN 0442155980

• Morss, Lester R., Norman M. Edelstein, and Jean Fuger. The Chemistry of the Actinide and Transactinide Elements. 3rd ed. 5 vols. Joseph J. Katz, adapter. Dordrecht: Springer, 2006. ISBN 1402035551

• Stwertka, Albert. Guide to the Elements. Rev. ed. Oxford: Oxford University Press, 1998. ISBN 0-19-508083-1

External links

All links retrieved November 8, 2022.

• Mendelevium The University of Sheffield and WebElements Ltd.
• It's Elemental: Mendelevium Jefferson Lab.

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