Californium
Californium is a synthetic radioactive metal best known for one isotope, californium-252, which is an unusually strong and convenient neutron emitter. That property has given it a genuine, if niche, set of real-world applications that most other elements this far down the periodic table simply don't have.
- Group · Period
- — · 7
- At room temp
- solid
- Melts at
- 1173 K
- Density
- Not yet available
- Discovered
- 1950
Uses
Californium is one of the few elements this deep into the actinides with genuine practical applications, almost all of them tied to one isotope, californium-252, which emits neutrons steadily and intensely. That makes it useful as a portable neutron source: it can help start up nuclear reactors, power neutron radiography that images the interior of dense objects non-destructively, and support oil and gas well logging, where a neutron source lowered into a borehole helps characterize the surrounding rock. Californium-252 has also been studied as a source for certain targeted cancer treatments, though this remains a specialized, limited application rather than a mainstream therapy.
History
Californium was discovered in 1950 by Stanley Thompson, Kenneth Street Jr., Albert Ghiorso, and Glenn Seaborg at Berkeley, who produced it by bombarding curium with alpha particles. It was named after the state of California and the University of California, continuing the string of discoveries the Berkeley team had been making throughout the 1940s. Unlike most of its neighbors on the periodic table, californium went on to find real practical use once larger quantities of californium-252 could be produced in specialized reactors.
Fun facts
- Californium-252 is such a reliable neutron emitter that only micrograms of it are needed to help start up a nuclear reactor.
- It's named directly after the state of California, honoring both the state and the University of California, where it was discovered.
- Californium-252 is used in oil and gas exploration, where portable neutron sources help analyze rock formations deep underground.
Frequently asked questions
Does californium have any real-world use?
Yes, more than most elements this heavy. Californium-252 is a strong, compact neutron source, which makes it useful for starting up nuclear reactors, for neutron radiography that images the inside of dense objects, for oil-well logging that probes underground rock formations, and in research into treating certain cancers.
Why is californium named after a US state?
It was discovered at the University of California, Berkeley, and the team chose to honor both the university and the state directly — unlike most elements, which are named after scientists, places tied to mythology, or minerals.
Is californium dangerous to be around?
Very. Californium-252 is an intense emitter of both neutrons and gamma radiation, so it's handled only in small amounts behind heavy shielding, and its practical uses rely on exactly that intensity being carefully contained.
Compounds
2 notable compounds containing Cf
- CfO2oxide
Californium dioxide
A black oxide representing californium's less common +4 oxidation state, identified alongside the more stable sesquioxide in trace laboratory samples. Characterizing it required some of the only californium ever produced in isolable quantities.
- CfCl3halide
Californium trichloride
A green crystalline solid and one of the best-characterized californium compounds, made by reacting californium oxide with anhydrous hydrogen chloride. It reflects californium's dominant +3 oxidation state in the solid state.
Isotopes
21 known isotopes
Swipe to see all columns →
| Isotope | Natural abundance | Half-life | Decay mode | Mass excess | Binding energy / nucleon | Decay width |
|---|---|---|---|---|---|---|
| Cf-249 | — | 351 Y | Alpha decay (100%), Spontaneous fission (5e-7%) | 69,722.73 keV | 7,483.4 keV | 4.12 × 10-26 eV |
| Cf-250 | — | 13.08 Y | Alpha decay (99.923%), Spontaneous fission (0.077%) | 71,170.34 keV | 7,479.96 keV | 1.11 × 10-24 eV |
| Cf-251 | — | 898 Y | Alpha decay (100%), Spontaneous fission | 74,134.98 keV | 7,470.5 keV | 1.61 × 10-26 eV |
Show all 21 isotopes
| Cf-236 | — | — | Unknown | — | — | — |
| Cf-237 | — | 2.1 s | Alpha decay (70%), Spontaneous fission (10%) | 57,938.26 keV | 7,503.35 keV | 2.17 × 10-16 eV |
| Cf-238 | — | 21.1 ms | Spontaneous fission (95%), Alpha decay (5%) | 57,278 keV | 7,509 keV | 2.16 × 10-14 eV |
| Cf-239 | — | 39 s | Electron capture, Alpha decay | 58,202 keV | 7,507 keV | 1.17 × 10-17 eV |
| Cf-240 | — | 0.96 m | Alpha decay (98%), Spontaneous fission (2%), Electron capture / beta-plus decay | 57,988.72 keV | 7,510.24 keV | 7.92 × 10-18 eV |
| Cf-241 | — | 3.78 m | Electron capture / beta-plus decay (75%), Alpha decay (25%) | 59,327 keV | 7,507 keV | 2.01 × 10-18 eV |
| Cf-242 | — | 3.5 m | Alpha decay (61%), Electron capture / beta-plus decay (39%), Spontaneous fission (0.014%) | 59,386.98 keV | 7,509.1 keV | 2.17 × 10-18 eV |
| Cf-243 | — | 10.7 m | Electron capture / beta-plus decay (86%), Alpha decay (14%) | 60,990 keV | 7,505 keV | 7.11 × 10-19 eV |
| Cf-244 | — | 19.4 m | Alpha decay (100%) | 61,478.1 keV | 7,505.14 keV | 3.92 × 10-19 eV |
| Cf-245 | — | 45.0 m | Electron capture (64.7%), Alpha decay (35.3%) | 63,385.15 keV | 7,499.66 keV | 1.69 × 10-19 eV |
| Cf-246 | — | 35.7 h | Alpha decay (100%), Electron capture (0.004%), Spontaneous fission (0.00024%) | 64,090.23 keV | 7,499.12 keV | 3.55 × 10-21 eV |
| Cf-247 | — | 3.11 h | Electron capture (99.965%), Alpha decay (0.035%) | 66,109.39 keV | 7,493.26 keV | 4.08 × 10-20 eV |
| Cf-248 | — | 333.5 d | Alpha decay (99.9971%), Spontaneous fission (0.0029%) | 67,237.95 keV | 7,491.04 keV | 1.58 × 10-23 eV |
| Cf-252 | — | 2.647 Y | Alpha decay (96.898%), Spontaneous fission (3.102%) | 76,034.61 keV | 7,465.35 keV | 5.46 × 10-24 eV |
| Cf-253 | — | 17.81 d | Beta-minus decay (99.69%), Alpha decay (0.31%) | 79,301.56 keV | 7,454.83 keV | 2.96 × 10-22 eV |
| Cf-254 | — | 60.5 d | Spontaneous fission (99.69%), Alpha decay (0.31%) | 81,341.4 keV | 7,449.23 keV | 8.73 × 10-23 eV |
| Cf-255 | — | 85 m | Beta-minus decay (100%) | 84,809 keV | 7,438 keV | 8.95 × 10-20 eV |
| Cf-256 | — | 12.3 m | Spontaneous fission (100%), Alpha decay (0.000001%) | 87,041 keV | 7,432 keV | 6.18 × 10-19 eV |