Californium is a radioactive element used in specialized neutron sources and research. It was first produced by bombarding curium with helium nuclei. Its story connects the creation of new elements to instruments that use nuclear emissions to investigate materials and their composition.
FROM ELEMENT TO APPLICATION
AN ELEMENT IN CONTEXT
Why is a californium neutron source different from reactor fuel?
Californium-252 neutron sources
FOLLOW THIS RELATIONSHIP
Name the source function
Californium-252 provides neutrons in specialized reactor startup applications. The source is an input to an engineered measurement and control setting, with a defined supporting role.
Explore the model (optional)
CfFORM → INTERACTION → CONSEQUENCE
Follow the explanation in either direction. These are authored steps, not a physical clock.
Optional: check your understanding
USE THE EXPLANATION
Which statement correctly describes the californium role?
Atomic identity, reference properties and structure models
INTERACTIVE 3D98 visible sites
An electron censusDrag to rotate · scroll or pinch to zoom
[Rn] 5f10 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.
Californium was discovered at Berkeley in 1950 by Stanley Thompson, Kenneth Street, Albert Ghiorso and Glenn Seaborg. The name honored California, continuing the local naming pattern begun with berkelium. Early work involved extremely small quantities; later production made specialized sources possible. Its history illustrates how a discovery first valued for extending the periodic table can acquire a practical role when one isotope has a useful signature.
1950
Discovery
The Berkeley team identifies californium.
1960
Larger samples become available
Production advances allow investigations using weighable quantities.
Californium for research and technology is manufactured in specialized facilities. It is not mined from natural deposits. Production yields a mixture requiring isotope and chemical characterization, and the element name alone does not specify output: californium-252 is selected for source applications because of its particular nuclear behavior.
Californium commonly forms +3 compounds, but its best-known applications exploit the spontaneous of californium-252. That isotope can release neutrons as its split. This is distinct from chemical bonding and should not be generalized to identical behavior from every californium isotope or every other radioactive element.
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
1173 K
at standard pressure unless noted
Boiling point
Not recorded
101.325 kPa
Density in g/cm³
15.1 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
608 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
1950 CEderived
WHERE IT SITS AMONG ITS NEIGHBORS
Electronegativity across period 7
Cf 1.3 Pauling · Californium
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.
