Californium - Cf
Atomic number : 98
CAS Registry Number: 7440-71-3
Relative Atomic Mass (12C = 12.0000) : 251.0796
Melting Point: about 900°C, 1170 K, 1652°F
Boiling Point: about 1,470°C ,1743 K, 2678°F
State (at room temperature (300 K)): Solid
Thermal Conductivity: 0.1 W/cm K
Group 3 actinide
Periodic Table Period: 7
Periodic Table Block: f-block
Density: 15.1 g/cm3
Electron Configuration: 1s2 2s2p6
Electrons per Energy Level: 2,8,18,32,28,8,2
Ionization Potential: V 6.3
Electronegativity (Pauling): 1.3
Ionic Radius: 0.934 Å
Filling Orbital: 5f 10
Number of Electrons (with no charge): 98
Number of Neutrons (most common/stable nuclide): 153
Number of Protons: 98
Oxidation States: 3 - main CfIII, others CfII, CfIV
Valence Electrons: 5f10 7s2
Valence Electron Potential (-eV): 44.5
Californium is an artificially produced, radioactive, silvery metal named
after the state of California and the University of California (USA). It was
first produced in 1950 by Glenn T. Seaborg, Stanley G. Thompson,
Albert Ghiorso, and Kenneth Street, Jr. They did it by bombarding microgram
quantities of 242Cm with 35 MeV helium ions (electrically charged
atoms) in the Berkeley 60-inch cyclotron. Specifically, they created
californium-245 (half-life 45 min).
Californium is a member of the actinide series of chemical elements and is
found in group IIIb of the periodic table. Its chemical properties are similar
to those of lanthanum. It is the sixth transuranium element to be synthesized,
and has yet to be found in the earth's crust. It did not even exist in weighable
amounts until ten years after they discovered it. The usual method of
preparation, that produces only milligram amounts, is neutron bombardment of
There are 18 known isotopes of californium with half-lives running from 40
seconds to 900 years.
The most stable californium isotope has a mass number of 251(half-life of 900
years). Californium-249 (half-life 351 years) is the most useful isotope when
dealing with chemical testing, and it is obtained by the decay of berkelium-249.
It's been used to create four solid compounds of californium; the trichloride,
oxychloride, oxyfluoride, and oxide.
Californium-252 (half-life 2.6 years) decays partially by nuclear fission and
emits neutrons and high amounts of energy. It is a very strong neutron emitter.
One microgram releases a toxic 170 million neutrons per minute. However, because
of the large number of neutron emissions, it has been useful in neutron moisture
gages, in well-logging (the determination of water and oil-bearing layers), as a
portable neutron source for discovery of metals such as gold or silver, and as a
source of neutrons for counters and electronic systems in industrial and medical
applications (such as cancer treatment). It is produced in nuclear reactors.
<-- Berkelium---Einsteinium -->
References and Further reading available at:
http://www.chemsoc.org/viselements/pages/data/californium_data.html - an EXCELLENT visual resource!