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| Atomic symbol: Cf |
| Atomic number: 98 |
| Atomic weight: (251) |
| Atomic volume: ? |
| Density: ? |
| Period Number: 7 |
| Group number: none |
| Group name: Rare Earth, Actinides |
| Element classification: Metal |
| Phase at room temperature: Solid |
| Melting Point: 1173.2 K |
| Boiling point: K |
| Heat of fusion: ? |
| Heat of vaporization: ? |
| Ionization Energy: 6.30 eV |
| 1st ionization energy: 608 kJ/mole |
| 2nd ionization energy: kJ/mole |
| 3rd ionization energy: kJ/mole |
| Electronegativity: 1.3 |
| Electron affinity: kJ/mole |
| Specific heat: ? |
| Heat atomization: kJ/mole atoms |
| Shells: 2,8,18,32,28,8,2 |
| Electron Shell Configuration: [Rn] 5f10 7s2 |
| Minimum oxidation number: 0 |
| Maximum oxidation number: 4 |
| Minimum common oxidation number: 0 |
| Maximum common oxidation no: 3 |
Appearance & Characteristics |
| Structure:: ? |
| Color: ? |
| Hardness: mohs |
| Toxicity: ? |
| Characteristics: Radioactive |
| Uses: neutron source |
| Reaction with air: ? |
| Reaction with 6M HCl: ? |
| Reaction with 15M HNO3: ? |
| Reaction with 6M NaOH: ? |
| Number of isotopes: 0 |
| Oxide(s): CfO Cf2O3 CfO2 |
| Hydride(s): ? |
| Chloride(s): CfCl3 |
| Atomic Radius: 186 pm |
| Ionic radius (1- ion): pm |
| Ionic radius (1+ ion): pm |
| Ionic radius (2- ion): pm |
| Ionic radius (2+ ion): pm |
| Ionic radius (3+ ion): 109 pm |
| Thermal conductivity: J/m-sec-deg |
| Electrical conductivity: 1/mohm-cm |
| Polarizability: 20.5 A^3 |
| Source: Synthetic |
| Relative abundance solar system: log |
| Abundance earth's crust: log |
| Estimated crustal abundance: Not Applicable |
| Estimated oceanic abundance: Not Applicable |
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| (State and University of California) Californium, the sixth transuranium element to be discovered, was produced by Thompson, Street, Ghioirso, and Seaborg in 1950 by bombarding microgram quantities of 242Cm with 35 MeV helium ions in the Berkeley 60-inch cyclotron. Californium (III) is the only ion stable in aqueous solutions, all attempts to reduce or oxidize californium (III) having failed. The isotope 249Cf results from the beta decay of 249Bk while the heavier isotopes are produced by intense neutron irradiation by the reactions. The existence of the isotopes 249Cf, 250Cf, 251Cf, and 252Cf makes it feasible to isolate californium in weighable amounts so that its properties can be investigated with macroscopic quantities. |
| Californium-252 is a very strong neutron emitter. One microgram releases 170 million neutrons per minute, which presents biological hazards. Proper safeguards should be used in handling californium. Reduction of californium to its metallic state has not yet been accomplished. Because californium is a very efficient source of neutrons, many new uses are expected for it. It has already found use in neutron moisture gauges and in well-logging (the determination of water and oil-bearing layers). It is also being used as a portable neutron source for discovery of metals such as gold or silver by on-the-spot activation analysis. 252Cf is now being offered for sale by the O.R.N.L. at a cost of $10/mg. As of May, 1975, more than 63 mg have been produced and sold. It has been suggested that californium may be produced in certain stellar explosions, called supernovae, for the radioactive decay of 254Cf (55-day half-life) agrees with the characteristics of the light curves of such explosions observed through telescopes. This suggestion, however, is questioned. |
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