Berkelium
Actinide · Period 7 · f-block
Named for its hometown, and a key to element 117
- Atomic mass
- 247 u
- State at 25 °C
- Solid
- Electronegativity
- 1.3
- Melting point
- 985.9 °C
- Boiling point
- 2,626.9 °C
- Configuration
- [Rn] 5f9 7s2
Nucleus drawn at reduced count for clarity. Drag to rotate.
Berkelium, explained
Video lesson in production
Bhavya’s explainer for this element will play here.
Overview
Berkelium is a soft, silvery, radioactive actinide metal with the configuration 5f9 7s2. Like most of the later actinides, it forms the Bk3+ ion in solution, but it can also be oxidised to Bk4+, which loses four electrons to reach a stable half-filled 5f7 shell. This mirrors terbium, the lanthanide directly above it, which also forms a +4 state. Bk4+ is a strong oxidising agent, a property used to separate berkelium from its neighbours.
Only about a gram of berkelium has been produced in the United States since the 1960s, so its chemistry has been studied with micrograms or less. Its most useful isotope, berkelium-249, has a 330-day half-life and is made in high-flux reactors by bombarding curium with neutrons for months. Berkelium-249 is valued mainly as a target: fired at with calcium-48 ions, it made tennessine, element 117, and as it decays it produces californium-249, another superheavy-element target.
Discovery
Stanley Thompson, Albert Ghiorso and Glenn Seaborg made berkelium in December 1949 at the University of California, Berkeley, by bombarding americium-241 with alpha particles in the 60-inch cyclotron. They identified the new element from milligrams of americium using ion-exchange chromatography. They named it after the city of Berkeley, just as terbium, the lanthanide above it, is named after the Swedish village of Ytterby.
- Where it’s found
- Berkelium does not occur in nature; it is produced in tiny quantities in high-flux reactors such as Oak Ridge's High Flux Isotope Reactor.
- What it’s used for
- Superheavy element synthesis
- Californium-249 production
- Actinide chemistry research
- Lanthanide–actinide comparisons
- In living things
- Berkelium has no biological role; absorbed berkelium accumulates in bone and is radiotoxic.
- Safety
- Highly radioactive and available only in microgram amounts in specialist laboratories. It must be handled in glove boxes to prevent internal exposure.
How it compares
Where Berkelium sits among all 118 elements on the trends that shape the table.
- Electronegativity1.3Pauling
#62 of 100 elements with data
- Ionization energy601kJ/mol
#66 of 104 elements with data
- Atomic radiusNo data
Not measured for this element
- Electron affinity-165kJ/mol
#108 of 109 elements with data
- Density14.8g/cm³
#22 of 114 elements with data
- Melting point1,260K
#49 of 110 elements with data
- Density
- 14.8 g/cm³
- Atomic radius
- —
- Covalent radius
- —
- Molar heat
- —
- Appearance
- silvery
- Discovered by
- Lawrence Berkeley National Laboratory
Inside the atom
97 electrons arranged in 7 shells: 2 · 8 · 18 · 32 · 27 · 8 · 2.
Orbital diagram
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f9 · shorthand [Rn] 5f9 7s2
- 1s2
- 2s2
- 2p6
- 3s2
- 3p6
- 4s2
- 3d10
- 4p6
- 5s2
- 4d10
- 5p6
- 6s2
- 4f14
- 5d10
- 6p6
- 7s2
- 5f9
Each box is an orbital holding up to two electrons of opposite spin. Highlighted subshells hold the valence electrons that decide how Berkelium bonds.
Signature reactions
The chemistry Berkelium is known for.
Nuclear · Alpha bombardment
Discovery of berkelium
Americium-241 absorbs an alpha particle and ejects two neutrons, forming berkelium-243 with a 4.5-hour half-life. The team detected it by its decay after separating it chemically.
Conditions: 35 MeV alpha particles from a cyclotron
Nuclear · Heavy-ion fusion
Making tennessine
A calcium-48 nucleus fuses with berkelium-249, and the compound nucleus sheds three neutrons to give tennessine-294. Other events shed four neutrons to give tennessine-293.
Conditions: calcium-48 beam on berkelium target
Nuclear · Beta decay
Beta decay of berkelium-249
Berkelium-249 slowly turns into californium-249 by emitting an electron. Stored berkelium targets therefore become contaminated with californium, which itself is used to make element 118.
Conditions: spontaneous; half-life 330 days
Where you’ll meet it
Berkeley, California
Berkelium is named after the city of Berkeley, where it was made in 1949.
Photo: Wikimedia Commons
Lawrence Berkeley National Laboratory
The Berkeley laboratory discovered berkelium and many other transuranium elements.
Photo: Wikimedia Commons
Albert Ghiorso
Albert Ghiorso co-discovered berkelium and eleven other elements.
Photo: Wikimedia Commons
High Flux Isotope Reactor
Oak Ridge's High Flux Isotope Reactor produced the berkelium used to discover tennessine.
Photo: Wikimedia Commons
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Research
No research on Berkelium yet
When Bhavya publishes a project that studies Berkelium, it will be linked here.