Editorial Feature

Californium (Cf) - Discovery, Occurrence, Production, Properties and Applications of Californium

Chemical Formula

Cf

Background

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.

Basic Information

Name Californium
Symbol Cf
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
Classification Metallic
Melting point 1173 K (900°C or 1652°F)
Boiling point Unknown
Density Unknown
Phase at room temperature Solid

Occurrence

Californium is not found in nature.

Isotopes

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.

Production

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.

Health Aspects

The following are some of the health effects of californium upon exposure to its radiation:

  • Genetic damage
  • Infertility/miscarriages
  • Leukemia
  • Cancer
  • Damage to immune system

Key Properties

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.

Applications

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.

References

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