Berkelium Element Facts - Atomic Number 97 or Bk

Berkelium Fun Facts, Properties, and Uses

This is the berkelium, dissolved, that was used to synthesize element 117.
ORNL, Department of Energy

Berkelium is one of the radioactive synthetic elements made in the cyclotron at Berkeley, California and the one that honors the work of this lab by bearing its name. It was the fifth transuranium element discovered (following neptunium, plutonium, curium, and americium). Here's a collection of facts about element 97 or Bk, including its history and properties:

Element Name


Atomic Number


Element Symbol


Atomic Weight


Berkelium Discovery

Glenn T. Seaborg, Stanley G. Thompson, Kenneth Street, Jr., and Albert Ghiorso produced berkelium in December 1949 at the University of California, Berkeley (United States). The scientists bombarded americium-241 with alpha particles in a cyclotron to yield berkelium-243 and two free neutrons.

Berkelium Properties

Such a small quantity of this element has been produced that very little is known about its properties. Most of the available information is based on predicted properties, based on the element's location on the periodic table. It is a paramagnetic metal and has one of the lowest bulk modulus values of the actinides. Bk3+ ions are fluorescent at 652 nanometers (red) and 742 nanometers (deep red). Under ordinary conditions, berkelium metal assumes hexagonal symmetry, transforming to a face-centered cubic structure under pressure at room temperature, and an orthorhombic structure upon compression to 25 GPa.

Electron Configuration

[Rn] 5f9 7s2

Element Classification

Berkelium is a member of the actinide element group or transuranium element series.

Berkelium Name Origin

Berkelium is pronounced as BURK-lee-em. The element is named after Berkeley, California, where it was discovered. The element californium is also named for this lab.


13.25 g/cc


Berkelium has a traditional shiny, metallic appearance. It is a soft, radioactive solid at room temperature.

Melting Point

The melting point of berkelium metal is 986 °C. This value is below that of neighbor element curium (1340 °C), but higher than that of californium (900 °C).


All of the isotopes of berkelium are radioactive. Berkelium-243 was the first isotope to be produced. The most stable isotope is berkelium-247, which has a half-life of 1380 years, eventually decaying into americium-243 via alpha decay. About 20 isotopes of berkelium are known.

Pauling Negativity Number


First Ionizing Energy

The first ionizing energy is predicted to be about 600 kJ/mol.

Oxidation States

The most common oxidation states of berkelium are +4 and +3.

Berkelium Compounds

Berkelium chloride (BkCl3) was the first Bk compound produced in sufficient quantity to be visible. The compound was synthesized in 1962 and weighed approximately 3 billionths of a gram. Other compounds which have been produced and studied using x-ray diffraction include berkelium oxychloride, berkelium fluoride (BkF3), berkelium dioxide (BkO2), and berkelium trioxide (BkO3).

Berkelium Uses

Since so little berkelium has ever been produced, there are no known uses of the element at this time aside from scientific research. Most of this research goes toward the synthesis of heavier elements. A 22-milligram sample of berkelium was synthesized at Oak Ridge National Laboratory and was used to make element 117 for the first time, by bombarding the berkelium-249 with calcium-48 ions at the Joint Institute for Nuclear Research in Russia. The element does not occur naturally, so additional samples must be produced in a lab. Since 1967, just over 1 gram of berkelium has been produced, in total.

Berkelium Toxicity

The toxicity of berkelium has not been well-studied, but it's safe to assume it presents a health hazard if ingested or inhaled, due to its radioactivity. Berkelium-249 emits low-energy electrons and is reasonably safe to handle. It decays in alpha-emitting californium-249, which remains relatively safe for handling, but does result in free-radical production and self-heating of the sample.

Berkelium Fast Facts

  • Element Name: Berkelium
  • Element Symbol: Bk
  • Atomic Number: 97
  • Appearance: Silvery metal
  • Element Category: Actinide
  • Discovery: Lawrence Berkeley National Laboratory (1949)


  • Emsley, John (2011). Nature's Building Blocks: An A-Z Guide to the Elements. New York, NY: Oxford University Press. ISBN 978-0-19-960563-7.
  • Peterson, J. R.; Fahey, J. A.; Baybarz, R. D. (1971). "The crystal structures and lattice parameters of berkelium metal". J. Inorg. Nucl. Chem. 33 (10): 3345–51. doi:10.1016/0022-1902(71)80656-5
  • Thompson, S.; Ghiorso, A.; Seaborg, G. (1950). "The New Element Berkelium (Atomic Number 97)". Physical Review. 80 (5): 781. doi:10.1103/PhysRev.80.781
  • Thompson, Stanley G.; Seaborg, Glenn T. (1950). "Chemical Properties of Berkelium". OSTI Technical Report doi:10.2172/932812
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Your Citation
Helmenstine, Anne Marie, Ph.D. "Berkelium Element Facts - Atomic Number 97 or Bk." ThoughtCo, Feb. 16, 2021, Helmenstine, Anne Marie, Ph.D. (2021, February 16). Berkelium Element Facts - Atomic Number 97 or Bk. Retrieved from Helmenstine, Anne Marie, Ph.D. "Berkelium Element Facts - Atomic Number 97 or Bk." ThoughtCo. (accessed June 5, 2023).