Berkelium
[Rn] 5f⁹ 7s² · 2 · 8 · 18 · 32 · 27 · 8 · 2
An actinide named after the city of Berkeley, by direct analogy with terbium and the village of Ytterby. Berkelium exists in microgram quantities, and its main role today is as a target for synthesising superheavy elements.
3D model
Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.
Drag to rotate, scroll to zoom
Atomic properties
- Atomic number
- 97
- Atomic mass
- 247 а.е.м. ≈
- Electron configuration
- [Rn] 5f⁹ 7s²
- Electrons per shell
- 2 · 8 · 18 · 32 · 27 · 8 · 2
- Block
- f-block
- Group
- no data
- Period
- 7
- Electronegativity (Pauling)
- 1.3
- Electronegativity (Allen)
- 1.3
- Atomic radius
- 244 pm
- Covalent radius
- 168 pm
- Van der Waals radius
- 244 pm
- Ionisation energy 1
- 601 kJ/mol
- Electron affinity
- -165.2 kJ/mol
- Common oxidation states
- +3
- Oxidation states
- +2, +3, +4, +5
Physical properties
- State at 25 °C
- solid
- Density
- 14.78 g/cm³
- Melting point
- 1 259 K · 985.9 °C
- Boiling point
- 2 900 K · 2 626.9 °C ≈
- Speed of sound
- no data
Thermal properties
- Heat of fusion
- 13 kJ/mol ≈
- Heat of vaporisation
- 310 kJ/mol ≈
- Specific heat capacity
- 0.08 J/(g·K)
- Thermal conductivity
- 10 W/(m·K) ≈
Mechanical properties
- Young's modulus
- no data
- Shear modulus
- no data
- Bulk modulus
- no data
- Poisson ratio
- no data
- Mohs hardness
- no data
- Brinell hardness
- no data
Electrical and magnetic properties
- Electrical resistivity
- 1 100 nΩ·m ≈
- Magnetic ordering
- paramagnetic
- Curie point
- no data
- Néel point
- no data
- Superconducting point
- no data
Crystal structure
- Crystal structure
- hexagonal close-packed (hcp)
- Lattice constants
- a = 341.6 pm · c = 1 106.9 pm
Abundance
- In the crust
- does not occur
- In the ocean
- does not occur
- In the universe
- does not occur
- In the human body
- does not occur
Isotopes
| Isotope | Abundance | Half-life | Decay mode |
|---|---|---|---|
| 247Bk | — | 1 380.04 yr | α |
| 249Bk | — | 329.98 d | β− |
Berkelium-247, half-life 1380 years, is the longest-lived, but practical work uses berkelium-249 at 330 days because it is what can be made.
Discovery
- Year of discovery
- 1949
- Discovered by
- Thompson, Ghiorso and Seaborg
- Where
- Berkeley, USA
- Origin of the name
- after Berkeley, by analogy with terbium named after Ytterby
History
Thompson, Ghiorso and Seaborg made berkelium in December 1949 on the Berkeley cyclotron by bombarding americium with alpha particles.
Where it occurs
Absent from nature.
How it is produced
In the Oak Ridge high-flux reactor by prolonged irradiation of curium. World output is under a milligram a year.
Role in living things
No biological role.
Safety
Extremely radiotoxic, handled only in hot cells.
Uses
- A target for superheavy element synthesis: tennessine was made at Dubna from berkelium-249
- Fundamental research in actinide chemistry
Curiosities
- Element 117, tennessine, was made from 22 milligrams of berkelium-249 bred at Oak Ridge over 250 days of irradiation.
- The berkelium target had to be flown from the United States to Dubna within days — part of it had already decayed in transit.
- Berkelium is named after a city on the model of terbium named after a village: the symmetry was deliberate.
- Less than a gram of berkelium has been made in all of history.