Berkelium

Berkelium is a radioactive synthetic actinide produced in microgram quantities. Named after Berkeley, California, where it was first made in 1949. It has no practical uses and is mainly a stepping stone in the synthesis of heavier elements.

• Atomic Number9797 protons, 97 electrons
• Atomic Mass247.07031 u97× heavier than hydrogen
• State at Room TempSolidSolid
• Density14 g/cm³
• Melting / Boiling1049.8°C
• Discovered1949

What is Berkelium?

Berkelium has 97 protons. Its most stable isotope, Bk-247, has a half-life of 1,380 years. Berkelium is produced in nanogram to microgram quantities at Oak Ridge and other nuclear facilities and is mainly used as a target to create element 103 (lawrencium) and transactinides. Produced in 1949 by Stanley Thompson, Glenn Seaborg, Albert Ghiorso and Kenneth Street Jr. at Berkeley.

Fact Berkelium is element 97, symbol Bk. As an actinide, it is part of the f-block of the periodic table: one of 15 radioactive elements from actinium (89) to lawrencium (103). All actinides are radioactive; none has a stable isotope. They are produced in nuclear reactors and by decay of heavier elements, and their chemistry has been studied using only microgram or nanogram quantities.

Where you find Berkelium

On Earth

Berkelium does not occur in significant natural abundance. It is produced only artificially, by bombarding heavier actinide targets with neutrons or lighter ions in nuclear reactors or particle accelerators. World production is measured in micrograms or milligrams per year.

How we use Berkelium

At element 97, practical applications are limited by the extreme difficulty of production and the intense radioactivity. Berkelium has 97 protons Future applications in targeted cancer radiotherapy are being investigated using alpha-emitting actinide isotopes bound to tumour-targeting molecules.

How it was discovered

Berkelium has 97 protons. Its most stable isotope, Bk-247, has a half-life of 1,380 years. Berkelium is produced in nanogram to microgram quantities at Oak Ridge and other nuclear facilities and is mainly used as a target to create element 103 (lawrencium) and transactinides. Produced in 1949 by Stanley Thompson, Glenn Seaborg, Albert Ghiorso and Kenneth Street Jr. at Berkeley.

Deeper dive: berkelium and the actinide series

The actinides (elements 89-103) form the lower of the two rows below the main body of the periodic table. They represent the filling of the 5f electron subshell. Unlike the lanthanides (the upper row), the actinides show greater variety in their chemistry because the 5f, 6d and 7s orbitals are close in energy. The early actinides, thorium through neptunium, can show many different oxidation states (e.g. uranium from +3 to +6). The heavier actinides increasingly resemble the lanthanides in preferring the +3 state.

All actinides beyond bismuth (83) are radioactive. The lightest, thorium, protactinium and uranium, have long enough half-lives to survive from the formation of the solar system. Neptunium and beyond are almost entirely synthetic, produced in nuclear reactors or accelerators. The transuranic elements were created at remarkable facilities including Oak Ridge National Laboratory, the Berkeley Cyclotron, the GSI in Darmstadt and JINR in Dubna.

Moving to 98 protons brings us to the next element on the periodic table.