ElementsWhat is berkelium?
Berkelium is a radioactive metal made in very small amounts in special reactors.
What is berkelium used for?
Research only, including making heavier elements such as tennessine.
Where the name comes from
From Berkeley, California, the city where it was first made.
Key facts
- Symbol
- Bk
- Atomic number
- 97
- Atomic mass
- 247.07031 u
- Family
- Actinide
- Period
- 7
- Group
- none (f-block)
- Block
- f
- State at room temperature
- Solid
- Melting point
- 1,050 °C (1,323 K, 1,922 °F)
- Boiling point
- not measured
- Density
- 14 g/cm³
- Electrons per shell
- 2, 8, 18, 32, 27, 8, 2
- Electron configuration
- [Rn]7s2 5f9
- Common oxidation states
- +4, +3
- Electronegativity (Pauling)
- 1.3
- First ionisation energy
- 6.23 eV
- Electron affinity
- no value
- Atomic radius (van der Waals)
- 244 pm
- Discovered
- 1949
Place in the periodic table
Berkelium is element number 97. It sits in period 7 (row 7) of the periodic table, in the separate row of actinides drawn below the main table, and belongs to the f-block. Just before it comes curium (96), and just after it comes californium (98).
Family: Actinides.
Physical properties
At room temperature berkelium is a solid. Its melting point is about 1,050 °C. Its boiling point has not been measured reliably. Its density is 14 grams per cubic centimetre, so a one-litre block would weigh about 14 kilograms. By density it ranks 12th among the 96 elements with a measured value.
Inside the atom
An atom of berkelium has 97 protons in its nucleus and, when neutral, 97 electrons around it. The electrons are arranged in 7 shells: 2, 8, 18, 32, 27, 8, 2. The outermost shell holds 2 electrons. Written in full, the electron configuration is [Rn]7s2 5f9.
Its electronegativity on the Pauling scale is 1.3. This number shows how strongly an atom pulls shared electrons towards itself: fluorine, the strongest, is 3.98. Removing one electron from an atom takes 6.23 electronvolts (about 601 kilojoules per mole). One mole of berkelium weighs 247.07031 grams, so a single gram contains about 2.44 × 1021 atoms.
The ring picture is a simple model that only counts the electrons in each shell. Real atoms do not look like this.
Next steps
- Work out the weight of a compound that contains berkelium with the molar mass calculator.
- Compare it with every other element in the sortable list.
- Test yourself with the symbol quiz.
Figures on this page are from PubChem (U.S. National Library of Medicine), as downloaded on 11 November 2026. See About and data sources.