Mendelevium

fermium – mendelevium – nobelium Tm Md        File:-TableImage.png Full table
Known properties
Name, Symbol, Number	Mendelevium, Md, 101
Chemical series	Actinides
Period, Block	7 , f
Appearance	unknown; probably metallic, silvery white or gray
Atomic weight	[258] amu
Electron configuration	[Rn]5f13 7s2
e- 's per energy level	2, 8, 18, 32, 31, 8, 2
State of matter	Presumably a solid
Most stable isotopes
iso NA half-life DM DE MeV DP 257Md {syn.} 5.52 h ε α SF 0.406 7.558   257Fm 253Es   258Md {syn.} 51.5 d ε 1.230 258Fm 260Md {syn.} 31.8 d SF α ε β-   7.000   1.000   256Es 260Fm 260No

Mendelevium (also known as unnilunium) is a synthetic element in the periodic table 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.

Notable 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. Md-256 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.

History

Mendelevium (for Dmitri Mendeleev) was first synthesized by Albert Ghiorso (team leader), Glenn T. Seaborg, Bernard Harvey, and Greg Choppin in early 1955. The team produced Md-256 (half-life of 76 minutes) when they bombarded an einsteinium-253 target with alpha particles (helium nuclei) in the Berkeley Radiation Laboratory's 60-inch cyclotron (Md-256 was synthesized one-atom-at-a-time). Element 101 was the ninth transuranic element synthesized.

Isotopes

15 radioisotopes of mendelevium have been characterized, with the most stable being Md-258 with a half-life of 51.5 days, Md-260 with a half-life of 31.8 days, and Md-257 with a half-life of 5.52 hours. All of the remaining radioactive isotopes have half-lifes that are less than 97 minutes, and the majority of these have half lifes that are less than 5 minutes. This element also has 1 meta state, 258m-Md (t_½ 57 minutes). The isotopes of mendelevium range in atomic weight from 245.091 amu (Md-245) to 260.104 amu (Md-260).

References

• Los Alamos National Laboratory - Mendelevium
• Guide to the Elements - Revised Edition, Albert Stwertka, (Oxford University Press; 1998) ISBN 0-19-508083-1
• It's Elemental - Mendelevium

External links

• WebElements.com - Mendelevium
• EnvironmentalChemistry.com - Mendelevium