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What is Californium

A radioactive metal, californium (pronounced as kal-eh-FOR-nee-em) belongs to the family of actinides and denoted by the chemical symbol Cf [1]. It undergoes reactions when heated with hydrogen, nitrogen, and halogens [3]. It has 20 isotopes out of which californium-251 has a half-life of 900 years [1, 3].



Origin of its Name: The element is named after the university and state of California where its discovery took place [1].

Who Discovered it: Stanley Thompson, Jr. Albert Ghiorso, Kenneth Street, and Glenn Seaborg were responsible for synthesizing californium [1].

When, Where, and How was Californium Discovered

In 1950 at Berkeley, California, a research team comprising of Thompson, Ghiorso, Street, and Seaborg targeted curium-242 with helium ions to produce californium-245 that had a half-life of 44 minutes along with a free neutron [1]. Overall, only 5000 atoms of the new element have been artificially synthesized.

Position of Californium on the Periodic Table [1]

Group Actinides
Period 7
Block f

Properties and Characteristics of the Element

General Properties

Relative atomic mass/weight 247 [1]
Atomic mass 247 atomic mass units [7]

Physical Properties

Color/appearance Silver white [3]
Odor Unknown [6]
Melting point/freezing point 900°C (1652°F) [1]
Boiling point Unknown [1]
Density 14.78 g/cm3 [1]
State at normal room temperature (solid/liquid/gas) Solid [1]
Thermal conductivity 10 W m-1 K-1 [3]

Chemical Properties

Flammability Unknown [6]
Oxidation states 4, 3 [1]

Atomic Data of Californium

 Atomic number 98 [1]
 Electron configuration (noble gas configuration) [Rn] 5f10 7s2 [1]
 Atomic structure
–  Number of Electrons  98 [3]
–  Number of Neutrons  153
–  Number of Protons  98

Radius of atom

       –  Atomic Radius  2.45 Å [1]
       –  Covalent Radius  1.68 Å [1]
Ionization energy [1]


1st 2nd 3rd 4th 5th 6th 7th
606.092 1138.5


Californium Bohr Model

What are the Uses of Californium

  • Since Cf is a source of neutrons, it’s used as a neutron emitter in nuclear reactors [1, 3] as well as in the identification of gold and silver ores through a process called neutron activation analysis [3, 5].
  • The ability of the element to generate high-energy neutrons makes it useful as a moisture gauge/meter to detect water layers in oil wells [3, 5].
  • It is found to be effective in the determination of metal stress in aircraft [1].
  • Californium is used in portable metal detectors [1].
  • Californium-252 might be useful in the cancer treatment of pelvic organs such as uterus, bladder, and rectum [3]. It is also sometimes used in jewelry making.

Californium Bullet

Dangerous Effects of Californium

Extended exposure to the metal might be hazardous though no studies have been able to show its carcinogenic effects on humans [3].

Interesting Facts

  • One microgram of californium-252 can generate 170,000,000 neutrons per minute [2].
  • The element was not available in weighable amounts until ten years after its discovery due to minute production in the laboratory [1].

Californium Element

Californium Price

As Cf is only produced in milligrams by bombarding neutrons with plutonium-239, it may not be available in the commercial market [1]. However, it has been speculated that the radioactive metal may cost about $27 million per gram if produced on a larger scale.



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