Berkelium is a radioactive actinide produced in specialized nuclear facilities. Berkelium-249 supplied the target for experiments that created tennessine, element 117. Its significance therefore includes enabling discovery: carefully prepared atoms of one rare element became starting material for investigating an even heavier one.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
Why was berkelium only one part of the evidence for tennessine?
Berkelium-249 target material in accelerator research
FOLLOW THIS RELATIONSHIP
Locate the target contribution
Berkelium-249 supplied a necessary research material for the tennessine experiments. In this exercise, distinguish the known input from the evidence needed to identify an output.
Explore the model (optional)
BkFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Optional: check your understanding
USE THE EXPLANATION
What additional evidence is needed beyond identifying the berkelium target?
Atomic identity, reference properties and structure models
INTERACTIVE 3D97 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Rn] 5f9 7s2. Grouping electrons by principal shell connects the neutral-atom configuration to periodic-table patterns.
What this representation means
A three-dimensional counting diagram. Dots are count markers, not measured electron positions; spherical placement and spacing are arbitrary. There are no electron trajectories here. Orbitals describe quantum states.
Stanley Thompson, Albert Ghiorso and Glenn Seaborg discovered berkelium in 1949 at Berkeley. Identification initially depended on radiation and chemical behavior at tracer scale, rather than a visible metal sample. Named for its city of discovery, berkelium later became both a chemical research subject and a stepping stone to tennessine. The interval between discovery and detailed bonding studies reflects how strongly scarcity limits research on heavy elements.
1949
Element identified
Berkeley researchers establish element 97.
1962
Compound prepared
Berkelium dioxide is prepared, extending study beyond the initial tracer observations.
Berkelium is manufactured in specialized nuclear facilities and has no mineable natural occurrence. Research quantities emerge from long actinide production and separation programs. Radioactive changes the available inventory during a project, so making the element and delivering a chemically suitable sample are separate challenges rather than a single event.
Berkelium can display both +3 and +4 chemistry. Experiments with particular binding molecules show how the chemical surroundings can stabilize the tetravalent form, distinguishing it from neighboring actinides under the same conditions. This observed behavior concerns a compound; the neutral-atom configuration is a separate reference description.
Each section links its supporting references. Descriptions and diagrams were authored for this atlas. Source checks completed. Source checks dated 2026-09-06.
CITE THIS PAGE
Family labels and the group-3 layout are teaching conventions. A table position does not establish an unknown bulk property. Electronic configurations refer to neutral atoms; ions and material environments require their own account.
Read each reference property together with its units, conditions and the reference information below.
Not yet recorded: electron affinity, second ionization energy, ground-state term symbol, van der waals radius, thermal conductivity, specific heat capacity, electrical resistivity, crystal structure, lattice parameter a, space group, abundance in seawater, abundance in the universe, annual production, supply-risk listing, hazard classification, biological role, cas registry number, pubchem cid, wikidata item. These families are declared and awaiting an ingestion run against the source each names; they are listed here rather than shown as empty rows.
Physical
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Phase at 20 °C
solid
293.15 K, 101.325 kPa
Melting point in K
1259 K
at standard pressure unless noted
Boiling point
Not recorded
101.325 kPa
Density in g/cm³
14.79 g/cm³
solids and liquids at 293 K; gases at 273 K and 101.325 kPa
Atomic and electronic
Intended reference: Pauling electronegativity scale · Widely tabulated; original in The Nature of the Chemical Bond
Electronegativity in Pauling
1.3 Pauling
Pauling scale
First ionization energy in kJ/mol
601 kJ/mol
gas-phase neutral atom, ground state
Covalent radius
Not recorded
single-bond covalent radius
Common oxidation states
+3
states met in ordinary compounds; not exhaustive
Occurrence and identity
Intended reference: CRC Handbook of Chemistry and Physics · CRC Press
Abundance in the crust
Not recorded
upper continental crust, mass fraction
Has stable isotopes
Noderived
Discovery year in CE
1949 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 7
Bk 1.3 Pauling · Berkelium
Electronegativity across period 7. Exact values.
Ra
0.9
Ac
1.1
Th
1.3
Pa
1.5
U
1.38
Np
1.36
Pu
1.28
Am
1.13
Cm
1.28
Bk
1.3
Cf
1.3
Es
1.3
Fm
1.3
Md
1.3
No
1.3
Lr
1.3
The trend uses the same reference-property values as the periodic table. Elements with no recorded value are left out of the line rather than drawn at zero.
