Mendelevium (Md)

Isotopes of Mendelevium 

Isotope Atomic Mass Half-life Mode of Decay Nuclear Spin
Md-255 255.09108 27 minutes α to Es-251;
EC to Fm-255; SF
Md-256 256.0941 1.30 hours α to Es-252;
EC to Fm-256; SF
No data available 
Md-257 257.09553 57 minutes α to Es-253;
EC to Fm-257; SF
Md-258 258.09857 51.50 days EC to Fm-258 8
Md-259 259.1005 1.60 hours α to Es-255; SF 7/2
Md-260 260.104 32 days EC to Fm-260;
α to Es-256;
ß- to No-260
No data available


Mendelevium is a radioactive rare earth metal named after the Russian chemist Dmitri Ivanovich Mendeleev, the “father of the Periodic Table.” It was discovered in 1955 by Glenn T. Seaborg, Albert Ghiorso, Bernard G. Harvey, Gregory R. Choppin and Stanley G. Thompson at the University of California - Berkeley, USA. The team produced Mendelevium-256 (with a half-life of 87 minutes) when they bombarded an Einsteinium-253 target with alpha particles (helium nuclei).

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). Medelevium-256 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.

Sixteen isotopes of mendelevium from mass 245 to 260 have been characterized, the most stable being Mendelevium-258, with a half-life of 51.5 days; Mendelevium-260, with a half-life of 31.8 days; and Mendelevium-257, 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.

Properties of Mendelevium

Name Mendelevium
Symbol Md
Atomic number 101
Atomic weight [258]
Standard state Presumably a solid at 298 °K
CAS Registry ID 7440-11-1
Group in periodic table N/A 
Group name Actinoid
Period in periodic table 7 (Actinoid)
Block in periodic table f-block
Color Unknown, but probably metallic and silvery white or grey in appearance
Classification  Metallic
Melting point  About 1100 °K [or 827 °C or 1521 °F]
Boiling point No data available
Density of solid No data available
Electron configuration [Rn]5f137s2

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