californium

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 Valence +3
Group 3 actinide
Periodic Table Period: 7
Periodic Table Block: f-block
Density: 15.1 g/cm³
Electron Configuration: 1s²   2s²p⁶   3s²p⁶d¹⁰   4s²p⁶d¹⁰f¹⁴   5s²p⁶d¹⁰f¹⁰   6s²p⁶   7s²
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 Cf^III, others Cf^II, Cf^IV
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 plutonium

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.

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Periodic Table