Mendelevium is a synthetic, highly radioactive actinide metal. It was first produced in 1955 (Berkeley) by bombarding einsteinium with alpha particles. Only trace amounts are made; bulk properties are largely unknown.
Mendelevium (Md) is a man-made actinide with atomic number 101. It was discovered in 1955 and named in honor of Dmitri Mendeleev, creator of the periodic table.
Md is located in the f-block (actinide series), period 7, between fermium (Fm) and nobelium (No). In chemistry it most commonly exhibits the +3 state (Md(III)); the +2 state (Md(II)) is also accessible and unusually stable enough to be exploited for separations in tracer-level chemistry.
It was created by bombarding einsteinium targets with alpha particles in a cyclotron, then isolating a few atoms by radiochemical methods. A stylized route is:
\(^{253}\mathrm{Es}(\alpha, n)\,^{256}\mathrm{Md}\)
A commonly cited ground-state configuration is [Rn] 5f13 7s2. In solution, Md(III) corresponds approximately to a 5f12 configuration, while reduction to Md(II) approaches 5f13, which helps explain the relative stability of the +2 state among late actinides.
Several isotopes exist with short half-lives (minutes to hours or days). Isotopes used in laboratory studies include Md-256 and neighboring mass numbers. Short half-lives limit accumulation to trace amounts and require rapid, on-line chemistry techniques.
Analogous to other trivalent actinides, Md forms Md(III) halides and oxo-complexes in solution (e.g., chloride, nitrate media). Under strongly reducing conditions, Md(II) species can be generated; this redox switch is used to separate Md from adjacent trivalent actinides in ion-exchange or solvent-extraction systems.
Outside of fundamental research there are no routine applications. The element is produced atom-by-atom, so it mainly serves to advance actinide chemistry, nuclear structure studies, and to refine rapid radiochemical separation methods.
Scientists use rapid radiochemical separations at tracer levels: ion-exchange columns, extraction chromatography, and redox tuning between Md(III) and Md(II). Detection relies on decay signatures (alpha/EC) and alpha spectroscopy rather than bulk physical measurements.
Yes. Md is a radiotoxic heavy metal. Although only minute quantities are handled, strict controls are required: glove boxes or hot cells, HEPA-filtered ventilation, remote tools, dosimetry, and compliant radioactive-waste procedures.
A representative production/decay relation is:
\(^{253}\mathrm{Es}(\alpha, n)\,^{256}\mathrm{Md}\)
\(^{256}\mathrm{Md} \;\to\; ^{252}\mathrm{Es} + \alpha\)
Actual branching can include electron capture (EC) and depends on the isotope.