History

(Dmitri Mendeleev) Mendelevium, the ninth transuranium element of the actinide series discovered, was first identified by Ghiorso, Harvey, Choppin, Thompson, and Seaborg in early in 1955 during the bombardment of the isotope ²⁵³Es with helium ions in the Berkeley 60-inch cyclotron. The isotope produced was ²⁵⁶Md, which has a half-life of 76 min. This first identification was notable in that ²⁵⁶Md was synthesized on a one-atom-at-a-time basis.

Isotopes

Fourteen isotopes are now recognized. ²⁵⁸Md has a half-life of 2 months. This isotope has been produced by the bombardment of an isotope of einsteinium with ions of helium. Eventually enough ²⁵⁸Md should be made to determine its physical properties.

Uses

²⁵⁶Md has been used to elucidate some of the chemical properties of mendelevium in aqueous solution.

Properties

Experiments seem to show that the element possesses a moderately stable dipositive (II) oxidation state in addition to the tripositive (III) oxidation state, which is characteristic of the actinide elements.

Picture: Dmitri Mendeleev

Sources: CRC Handbook of Chemistry and Physics and the American Chemical Society.

Last Updated: 12/15/2003, � Chemistry Operations

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