Californium was discovered in 1950 by a team consisting of Glenn Seaborg, Albert Ghiorso, Kenneth Street and Stanley G. Thompson at the University of California while performing an experiment of bombarding curium-242 with alpha-particles using a 60-inch cyclotron. The nuclear reaction produced very small quantities of californium-245 and a free neutron. The element derived its name from the University of California where the experiment was conducted.
||Solid at 298 K
|CAS Registry ID
|Period in periodic table
|Block in periodic table
||Unknown, but probably metallic and silvery white or grey in appearance
||1173 K (900°C or 1652°F)
|Phase at room temperature
Californium is not found in nature.
Californium has 20 isotopes with known half-lives and mass numbers ranging from 237 to 256. All the isotopes are radioactive. The most stable isotopes of californium are listed below:
- 251Cf with a half-life of 898 years
- 249Cf with a half-life of 351 years
- 250Cf with a half-life of 13.08 years
- 252Cf with a half-life of 2.6 years.
Exceptionally, 252Cf has a strange characteristic of releasing neutrons upon breakage.
Californium is produced in particle accelerators and nuclear reactors. Bombardment of berkelium-249 with neutron forms berkelium-250 which beta decays to produce californium-250. Californium-250, when bombarded with a neutron produces californium-251 and californium-252. Irradiation of curium isotopes with neutron in nuclear reactors also produces californium-252. Few mg of californium-252 and μg of californium-249 can be obtained by prolonged exposure of plutonium and americium with neutrons.
The following are some of the health effects of californium upon exposure to its radiation:
- Genetic damage
- Damage to immune system
The key properties of californium include the following:
- It is a soft, malleable metal
- It is highly radioactive
- It is a strong neutron emitter
- It is fairly reactive as it rapidly forms into an oxide when exposed to air
- It exhibits the properties of lanthanides.
Some of the applications of californium are listed below:
- It is used for treating cancer
- It is used as a neutron source for identifying silver and gold ores
- It finds use in neutron moisture gauges for measuring moisture content of soil
- It is also used for inspecting airline baggage.