Nobelium
actinideProperties
| Property | Value |
|---|---|
| Atomic Mass | 259 amu |
| Category | actinide |
| Period | 7 |
| Electron Configuration | [Rn] 5f14 7s2 |
| Electronegativity | 1.3 (Pauling) |
| Oxidation States | 3, 2 |
| Melting Point | 1100 K (826.9 °C) |
| Discovered By | Joint Institute for Nuclear Research (Dubna) (1966) |
About Nobelium
Nobelium is the actinide that breaks the actinide pattern. Across the rest of the series the +3 oxidation state dominates aqueous chemistry, but in nobelium the filled 5f¹⁴ shell sits low enough in energy that the metal prefers to give up only its two 7s electrons. The result is a +2 aqueous ion that behaves more like an alkaline earth than a heavy actinide — a direct parallel to ytterbium at the bottom of the lanthanide row, where the same 4f¹⁴ closure pulls the same trick. Confirming this on a few hundred atoms at a time required cation-exchange chromatography on No²⁺ extracted from heavy-ion bombardments at Dubna and Berkeley, which is the kind of experimental athleticism that defines superheavy chemistry. The most stable isotope is ²⁵⁹No with a 58-minute half-life. The discovery itself is a textbook case in IUPAC priority disputes: Stockholm, Berkeley and Dubna all claimed it through the late 1950s and 1960s before the credit settled on Dubna in 1997.
Fun Fact
Nobelium's discovery sparked one of the bitterest priority disputes in the history of science, with three countries claiming credit over nearly a decade — the controversy was not fully resolved until 1997, over 30 years after the initial claims.
Common Uses
- Cation-exchange chromatography studies of the +2 actinide oxidation state
- Benchmarking relativistic actinide-series calculations against experiment
- Heavy-ion fusion reaction studies at Dubna and GSI
- Probing 5f shell stability at the end of the actinide row
- No commercial use — exists only in atom-at-a-time quantities