Berkelium (Bk)
Element 97 · Actinide · atomic mass [247] u · f-block, period 7
Electron shells: 2, 8, 18, 32, 27, 8, 2
Berkelium exists only in microgram quantities and has no use outside the laboratory. Its main role has been as a target for making even heavier elements.
A 22-milligram sample of berkelium — one of the largest ever made — was used to create element 117.
- Atomic number
- 97
- Atomic mass
- [247] u
- Electron configuration
- [Rn] 7s² 5f⁹
- Group · period · block
- f-block · 7 · f
- Oxidation states
- +3, +4
- Electronegativity
- 1.3 (Pauling)
- Melting point
- 1,050 °C
- Boiling point
- —
- Density
- 14 g/cm³
- State at 20 °C
- Solid
- Appearance
- Silvery metal
- Discovered
- Glenn T. Seaborg, Stanley Thompson and Albert Ghiorso, 1949
97 protons, and 97 electrons when neutral
Mass number of the longest-lived isotope — no standard atomic weight exists
Shown in the strip below the table
What Berkelium is used for
- Target material for synthesising tennessine
- Nuclear research
Atomic structure of Berkelium
A neutral berkelium atom has 97 protons and 97 electrons. Its most common isotope carries about 150 neutrons, which is where the mass number 247 comes from. Change the neutron count and you have a different isotope of berkelium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 32, 27, 8, 2. In orbital notation that is [Rn] 7s² 5f⁹. As a f-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Berkelium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Berkelium sits in the periodic table
The second f-block row, elements 89-103. All are radioactive, and everything past uranium is essentially man-made.
- One proton lighter: Curium.
- One proton heavier: Californium.
Discovery and naming
Berkelium was discovered by Glenn T. Seaborg, Stanley Thompson and Albert Ghiorso in 1949. Its name comes from Berkeley, California, which is also why its symbol (Bk) does not match its English name.
Every isotope of berkelium is radioactive, so it has no standard atomic weight. Periodic tables show the mass number of its longest-lived isotope in square brackets instead.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Berkelium?
Berkelium has no stable isotope, so it has no standard atomic weight. Periodic tables instead show 247 in square brackets — the mass number of its longest-lived isotope.
How many protons, neutrons and electrons does Berkelium have?
Berkelium has 97 protons, because the atomic number is the proton count and that is what makes an atom Berkelium at all. A neutral Berkelium atom has the same number of electrons, 97. The neutron count varies by isotope; the most common one has about 150, since 247 − 97 = 150.
What is the electron configuration of Berkelium?
The electron configuration of Berkelium is [Rn] 7s² 5f⁹. Its electrons are arranged 2, 8, 18, 32, 27, 8, 2 across 7 shells.
Is Berkelium a metal?
Yes. Berkelium is classified as a actinide, on the metallic side of the table.
What group and period is Berkelium in?
Berkelium sits in the f-block strip below the main table, in period 7, among the actinides. Elements in that strip are not given a group number in the standard 18-column layout.
What is the charge of Berkelium?
Berkelium most commonly forms a 3+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound. Across all its compounds it shows oxidation states of +3, +4.
What is the melting point of Berkelium?
Berkelium melts at 1,050 °C. That puts it in the solids at everyday temperatures.
What is Berkelium used for?
Target material for synthesising tennessine, Nuclear research. Berkelium exists only in microgram quantities and has no use outside the laboratory.
Who discovered Berkelium, and where does its name come from?
Berkelium (Bk) was discovered by Glenn T. Seaborg, Stanley Thompson and Albert Ghiorso in 1949. The name comes from Berkeley, California.
Is Berkelium radioactive?
Yes. Every isotope of Berkelium is radioactive — it has no stable form at all, which is why the periodic table shows its mass in square brackets rather than as a standard atomic weight.