Mendelevium
Element 101 · Actinide
Mendelevium was the first element ever synthesized one atom at a time, by bombarding einsteinium-253 with alpha particles in 1955. Only a few atoms were made in the discovery experiment. It is intensely radioactive with a half-life of under two months for its longest-lived isotope. Unusually for an actinide, mendelevium has a relatively stable +2 oxidation state in solution, resembling its lanthanide counterpart ytterbium. Properties are predicted, with very limited experimental data.
Key facts
| Atomic number | 101 |
|---|---|
| Atomic weight | [258] |
| Category | Actinide |
| Group / Period | — / 7 |
| Block | f |
| Electron configuration | [Rn] 5f13 7s2 |
| Common oxidation states | +3, +2 |
| State at STP | Solid |
| Electronegativity | 1.3 |
| Melting point | 827 °C (estimated) |
Occurrence
Mendelevium is entirely synthetic, produced atom-by-atom in particle accelerators. It has no natural occurrence and no weighable samples exist.
Applications
One-atom-at-a-time studies of heavy-element chemistry
Research on relativistic effects in superheavy atoms
No commercial applications
Common compounds
- Mendelevium(II) chloride (MdCl2, tracer scale)
- Mendelevium(III) fluoride (MdF3, tracer scale)
Mendelevium was named after Dmitri Mendeleev, creator of the periodic table, and was the first element produced literally one atom at a time.
Data source: IUPAC standard atomic weights 2021