Californium

98

Cf

(251)

  • Name: Californium
  • Symbol: Cf
  • Atomic number: 98
  • Atomic weight: (251)
  • CAS Registry ID: 7440-71-3
  • Group name: Actinoid
  • Period number: 7
  • Block: f-block
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Description

Californium is a synthesized chemical element in the actinide family. It is a radioactive transuranic element that is a silver colored solid in its isolated form. Californium is still being studied as this element is relatively new; not much is known about it and it does not yet have any commercial uses. Californium has an atomic weight of 251, a melting point of 1652 °F, and the boiling point is not yet known. It is a radioactive element and dangerous to human health.

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Isolation

Californium is not found free in nature and it must be synthesized in order to be studied. Isolation procedures for this element continue to be studied.

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Currently californium is synthesized by bombarding the element curium with alpha particles. The alpha particles contain two protons and two neutrons in a compound that resembles the nucleus of helium; these particles are created through the alpha decay process of such elements as uranium and radium. Isotopes of californium can be created by using intense neutron radiation on an element such as berkelium; this procedure has to be carried out in a nuclear reactor. Some compounds of californium that have been isolated include californium oxychloride, californium oxide, and californium trichloride. The californium (III) cation has been shown to be stable in aqueous solutions. Californium was first synthesized in a cyclotron at Berkeley; the process consisted of bombarding the 242-isotope of curium with alpha particles; this process produced an isotope of californium, number 245, that had a half life of 44 minutes. While this synthesis processes are effective at producing californium, it is currently not produced on a large scale as it is too expensive, ($27 million per gram), and hazardous.


General
Name Californium
Symbol Cf
Number 98
Chemical series actinides
Group n/a
Period 7
Block f
Appearance silvery
Standard atomic weight (251)  g·mol−1
Electron configuration [Rn] 5f10 7s2
Electrons per shell 2, 8, 18, 32, 28, 8, 2
Atomic properties
Crystal structure
Oxidation states 2, 3, 4
Electronegativity 1.3 (scale Pauling)
Ionization energies 1st: 608 kJ/mol
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Atomic radius
Atomic radius (calc.)
Covalent radius
Van der Waals radius
Physical properties
Phase solid
Density (near r.t.) 15.1  g·cm−3
Liquid density at m.p.
Melting point 1173 K (900 °C, 1652 °F)
Boiling point
Critical point
Heat of fusion
Heat of vaporization
Heat capacity
Miscellaneous
Magnetic ordering
Electrical resistivity
Thermal conductivity
Thermal expansion
Speed of sound (thin rod)
Young's modulus
Shear modulus
Bulk modulus
Poisson ratio
Mohs hardness
Vickers hardness
Brinell hardness
CAS registry number 7440-71-3

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