mendelevium

/men'dl ee"vee euhm/, n. Chem., Physics.

a transuranic element. Symbol: Md, Mv; at. no.: 101.

[1950-55; named after D. I. MENDELEEV; see -IUM]

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▪ chemical element

 (Md),  

 synthetic chemical element of the actinoid series of the periodic table, atomic number 101. It was the first element to be synthesized and discovered one atom at a time. Not occurring in nature, mendelevium (as the isotope mendelevium-256) was discovered (1955) by Albert Ghiorso, Bernard G. Harvey, Gregory R. Choppin, Stanley G. Thompson, and Glenn T. Seaborg at the University of California, Berkeley, as a product resulting from the helium-ion bombardment of a minute quantity (1,000,000,000 atoms) of einsteinium-253 (atomic number 99).

      In about a dozen repetitions of the experiment, the team of scientists produced 17 atoms of mendelevium, which were identified by the ion-exchange adsorption–elution method (mendelevium behaved like its rare-earth homologue thulium). Other isotopes of mendelevium, all radioactive, have been discovered. The stablest is mendelevium-258 (two-month half-life). Studied by means of radioactive tracer techniques, mendelevium exhibits a predominant +3 oxidation state, as would be expected by its position in the actinoid series; a moderately stable +2 oxidation state is also known.

atomic number

101

stablest isotope

258

oxidation states

+2, +3

electronic config.

[Rn]5f¹³7s²

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