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.
Atomic number 98
Atomic weight 251 amu
Standard state Solid at 298 K
CAS Registry ID 7440-71-3
Group name Actinoid
Period in periodic table 7
Block in periodic table f-block
Color Unknown, but probably metallic and silvery white or grey in appearance
Melting point 1173 K (900°C or 1652°F)
Boiling point Unknown
Phase at room temperature Solid
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.
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:
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.