Californium (Cf)
Actinide · Radioactive · Synthetic
Californium is a prodigious neutron emitter — a microgram of Cf-252 releases millions of neutrons per second. That makes it valuable for starting up reactors, finding water and oil underground, and scanning cargo.
Position on the periodic table
Atomic properties
| Atomic number | 98 |
|---|---|
| Atomic mass | 251 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f10 |
| Noble gas shorthand | [Rn] 5f10 7s2 |
| Electrons per shell | 2, 8, 18, 32, 28, 8, 2 |
| Valence electrons (outer shell) | 2 |
| Common oxidation states | +3 |
| Electronegativity (Pauling) | 1.3 |
| Covalent radius (approx.) | Not available |
| First ionization energy | 608 kJ/mol |
| Electron affinity | -97.3 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 15.1 g/cm³ |
| Melting point | 899.85 °C (1173 K) |
| Boiling point | 1469.8 °C (1743 K) |
| Appearance | silvery |
| Radioactive | Yes |
| Origin | Synthetic (lab-made) |
Electron configuration of californium
Californium's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f10, usually shortened to [Rn] 5f10 7s2. Its electrons occupy 7 shells (2, 8, 18, 32, 28, 8, 2), placing it in period 7 of the f-block. Explore it interactively in the electron configuration calculator.
Uses of californium
- Portable neutron sources
- Reactor start-up neutron sources
- Neutron activation analysis and cargo scanning
- Oil-well logging
Biological role: None.
Occurrence: Entirely synthetic.
Common compounds of californium
Cf2O3
Californium(III) oxide
History and discovery
Discovered: 1950 — Lawrence Berkeley National Laboratory. Name origin: Named after California and its university.
Thompson, Street, Ghiorso and Seaborg made californium in 1950 from curium targets.
Safety notes
A strong neutron emitter — among the most hazardous materials to handle without heavy shielding.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Californium
1. What is the chemical symbol of Californium?
2. What is the atomic number of Californium?
3. Which category does Californium belong to?
4. What is the state of Californium at room temperature?
5. Which period of the periodic table is Californium in?
Californium FAQs
What is the atomic number of californium?
Californium's atomic number is 98 — every californium atom has 98 protons in its nucleus.
What is the symbol for californium?
Cf. Named after California and its university.
Is californium a metal, nonmetal, or metalloid?
Californium is classified as a actinide.
What state is californium at room temperature?
At about 25 °C, californium is a solid. It melts at 899.85 °C.
What is californium used for?
Key uses include: portable neutron sources; reactor start-up neutron sources; neutron activation analysis and cargo scanning.
Related elements
Keep working with this element
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