Berkelium
actinideProperties
| Property | Value |
|---|---|
| Atomic Mass | 247 amu |
| Category | actinide |
| Period | 7 |
| Electron Configuration | [Rn] 5f9 7s2 |
| Electronegativity | 1.3 (Pauling) |
| Oxidation States | 4, 3 |
| Melting Point | 1259 K (985.9 °C) |
| Boiling Point | 2900 K (2626.8 °C) |
| Density | 14.78 g/cm³ |
| Discovered By | Glenn T. Seaborg, Albert Ghiorso, Stanley G. Thompson (1949) |
About Berkelium
Berkelium is one of those actinides whose entire global stockpile fits in a small vial and whose chemistry has mostly been worked out a few atoms at a time. Bk-249 is the workhorse isotope, made by hammering Cm-244 with neutrons in the High Flux Isotope Reactor at Oak Ridge for roughly two years, then spending another six months separating it from a monstrous mixture of californium, curium, and fission products. The pull is that berkelium is one of the few actinides that climbs cleanly to the +4 oxidation state in solution — Bk(IV)/Bk(III) sits around +1.6 V — which makes it a useful redox handle for separation chemistry and a probe for relativistic 5f bonding effects that get sharp once you cross atomic number 95. The 2010 tennessine campaign at JINR Dubna leaned entirely on a 22.2 mg sample of Bk-249 shipped from Oak Ridge in a heavily shielded cask; bombarded with Ca-48 ions for six months, that target produced six atoms of element 117 and confirmed an isotope of the thus-far heaviest synthesized halogen homolog. The sample had a 320-day window of useful purity before Bk-249 beta-decayed into Cf-249.
Fun Fact
Creating enough berkelium to discover a new element required 250 days of continuous nuclear reactor irradiation, 90 days of chemical separation, and the combined expertise of two national laboratories — all for a sample smaller than a grain of sand.
Common Uses
- Heavy-ion target material for synthesis of element 117 (tennessine)
- Bk(IV)/Bk(III) redox standard for actinide separation chemistry research
- Probe for 5f-electron behavior and relativistic bonding studies
- Reference actinide for solvent extraction and ion-exchange method development
- Spectroscopy reference for atomic and crystal-field actinide measurements