Atomic Number: 101
Atomic Weight: 258.1
Discovery: G.T. Seaborg, S.G. Tompson, A. Ghiorso, K. Street Jr. (1955, United States)
Electron Configuration: [Rn] 7s2 5f13
Word Origin: Named in honor of Dmitri Mendeleev, who devised a periodic table of the elements
Isotopes: Fourteen isotopes have been recognized.
Properties: Mendelevium is the ninth transuranium element of the actinide series. Experiments indicate that mendelevium has a moderately stable dipositive (II) oxidation state in addition to the tripositive (III) oxidation state, as is characteristic of the actinide elements.
Uses: Md-256 has been used to determine some of the chemical properties of mendelevium in aqueous solution.
Sources: Mendelevium first was produced during the bombardment of Es-253 with helium ions in the Berkeley 60-inch cyclotron. The isotope produced was Md-256, with a half-life of 76 min. Md-256 was synthesized on a one-atom-at-a-time basis.
Element Classification: Radioactive Rare Earth Element (Actinide Series)
Melting Point (K): 1100
Appearance: Radioactive, synthetic metal
Atomic Radius (pm): 287
Pauling Negativity Number: 1.3
First Ionizing Energy (kJ/mol): (635)
Oxidation States: 3
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952), CRC Handbook of Chemistry & Physics (18th Ed.)
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