Mendelevium
actinideProperties
| Property | Value |
|---|---|
| Atomic Mass | 258 amu |
| Category | actinide |
| Period | 7 |
| Electron Configuration | [Rn] 5f13 7s2 |
| Electronegativity | 1.3 (Pauling) |
| Oxidation States | 3, 2 |
| Melting Point | 1100 K (826.9 °C) |
| Discovered By | Albert Ghiorso, Glenn T. Seaborg, Bernard G. Harvey, Gregory R. Choppin, Stanley G. Thompson (1955) |
About Mendelevium
Mendelevium is element 101, named for Dmitri Mendeleev, who built the framework that made it possible to predict where a new element would land before anyone made it. Berkeley produced the first atoms in 1955 by bombarding einsteinium-253 with alpha particles in the 60-inch cyclotron — the entire discovery rested on detecting just 17 atoms, washed off the catcher foil and pushed through ion-exchange chromatography to identify the element by elution order. That made Md the first element ever identified one atom at a time, a methodology that became the template for everything heavier. The longest-lived isotope, Md-258, has a half-life of 51.5 days, which is unusually long for the late actinides. Single-atom solution chemistry has shown Md prefers the +2 state in aqueous reduction conditions — most other actinides cling to +3 — which fits the picture of a nearly filled 5f shell stabilizing the divalent ion the way Eu²⁺ and Yb²⁺ do in the lanthanide series.
Fun Fact
Mendelevium was the first element ever discovered one atom at a time — in the original 1955 experiment, only 17 atoms were produced, yet that was enough for the team to positively identify a brand new element through chemical analysis.
Common Uses
- First element discovered atom-by-atom — methodology benchmark
- Single-atom aqueous chemistry probing actinide +2/+3 redox
- Ion-exchange elution comparisons across the actinide series
- Reference data for late-actinide 5f shell stabilization
- No commercial applications