Berkelium
Atomic Data
| Atomic Number | 97 |
| Symbol | Bk |
| Atomic Weight | 247 u |
| Density (STP) | 14.0 g/cm³ |
| Melting Point | 985.85 °C (1259 K) |
| Boiling Point | 2626.85 °C (2900 K) |
| Electronegativity | 1.3 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f9 6s2 6p6 7s2 |
| Oxidation States | +3, +4 |
| Phase at STP | Solid |
| Category | Actinoid |
| Period / Group | 7 / None |
| CAS Number | 7440-40-6 |
Electron Configuration
[Rn] 5f9 7s2
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 10 | 46 |
| N | 4 | 4f | 14 | 60 |
| O | 5 | 5s | 2 | 62 |
| O | 5 | 5p | 6 | 68 |
| O | 5 | 5d | 10 | 78 |
| O | 5 | 5f | 9 | 87 |
| P | 6 | 6s | 2 | 89 |
| P | 6 | 6p | 6 | 95 |
| Q | 7 | 7s | 2 | 97 |
| Total | 97 | 97 | ||
Isotopes of Berkelium
Berkelium has two naturally occurring stable isotopes. The most abundant is ²⁴⁷Bk, comprising None% of all naturally occurring Berkelium.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Berkelium-247 | ²⁴⁷Bk | 97 | 150 | trace | Stable |
| Berkelium-249 | ²⁴⁹Bk | 97 | 152 | trace | Stable |
Abundance & Occurrence
Berkelium is present in Earth's crust at approximately trace amounts by mass and at approximately trace amounts by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Radioactivity: Berkelium-249 (t½ = 330 days, beta emitter) and its daughter Cf-249 (an alpha emitter) create a complex mixed radiation environment; internal contamination is a primary hazard.
- Extreme scarcity: specialised handling: Berkelium is produced only at Oak Ridge National Laboratory in milligram quantities; all handling occurs in hot cells or lead-shielded glove boxes by trained radiochemists.
- Decay chain hazard: Bk-249 decays to Cf-249, a strong alpha emitter; samples must be monitored for ingrowth of californium during storage and use.
- Regulatory controls: Possession of berkelium requires national nuclear regulatory licensing; quantities are subject to strict nuclear material accountancy.
Berkelium in the Real World
Real-World Uses
- Synthesis of tennessine (element 117): Berkelium-249 (t½ = 330 d), produced in milligram quantities in the High Flux Isotope Reactor at Oak Ridge National Laboratory, was used as the target material in the 2010 nuclear reaction that first synthesised element 117 (tennessine) at the JINR Dubna accelerator.
- Actinide chemistry research: Berkelium is studied to understand the transition from light to heavy actinide electronic structure; experiments on its solution chemistry, solid-state compounds, and oxidation states (Bk³⁺, Bk⁴⁺) inform models of the actinide series and nuclear waste behaviour.
- Production of heavier elements: Bk-249 is a key target isotope in the synthesis of elements 117 and beyond; the limited availability of mg-scale Bk-249 is a major bottleneck in superheavy element research programmes worldwide.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is berkelium used for?
Berkelium has no practical uses. Its most significant role was as a target material in the synthesis of heavier elements: tennessine (element 117) was synthesised in 2010 by bombarding berkelium-249 targets with calcium-48 ions at JINR in Russia. The production of the 22 milligrams of Bk-249 required for that experiment took 250 days of irradiation at Oak Ridge National Laboratory and was a major logistical and scientific undertaking.
How many atoms of berkelium have been made?
Berkelium is produced only in milligram quantities over months of irradiation at high-flux nuclear reactors. The total world production of berkelium since its discovery is measured in grams: primarily at Oak Ridge National Laboratory's High Flux Isotope Reactor. The longest-lived isotope, Bk-247, has a half-life of 1380 years, but the most easily produced, Bk-249, has a half-life of only 330 days, limiting its useful lifetime.
How was berkelium discovered?
Berkelium was synthesised in December 1949 at the University of California, Berkeley, by Stanley Thompson, Albert Ghiorso, and Glenn Seaborg. They bombarded americium-241 with helium ions (alpha particles) in a 60-inch cyclotron to produce berkelium-243. It was named after Berkeley, California, and the University of California, Berkeley, following the precedent set by californium (named for California and UC).
Is berkelium radioactive?
Yes, all isotopes of berkelium are radioactive. Berkelium has no stable isotopes. The longest-lived isotope, Bk-247, decays by alpha emission with a half-life of 1,380 years. The most commonly produced isotope, Bk-249, decays by beta emission with a half-life of 330 days. Because of its intense radioactivity, berkelium must be handled in specialised hot cells with remote-handling equipment.