[General | States | Energies | Oxidation & Electrons]
[Appearance & Characteristics | Reactions | Other Forms]
[Radius | Conductivity
| Abundance | History]
| Name |
Californium |
Symbol |
Cf |
| Atomic number |
98 |
Atomic weight |
(251) |
| Density @ 293 K |
? |
Atomic volume |
? |
| Group |
Rare Earth, Actinides |
Discovered |
1949 |
| State (s, l, g) |
|
| Melting point |
1173.2 K |
Boiling point |
K |
| Heat of fusion |
? |
Heat of vaporization |
? |
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| 1st ionization energy |
608 kJ/mole |
Electronegativity |
1.3 |
| 2nd ionization energy |
kJ/mole |
Electron affinity |
kJ/mole |
| 3rd ionization energy |
kJ/mole |
Specific heat |
? |
| Heat atomization |
kJ/mole atoms |
| Shells |
2,8,18,32,28,8,2 |
Electron configuration |
[Rn] 5f10 7s2 |
| Minimum oxidation number |
0 |
Maximum oxidation number |
4 |
| Minimum common oxidation number |
0 |
Maximum common oxidation number |
3 |
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| Structure |
|
Color |
|
| Uses |
neutron source |
Toxicity |
|
| Hardness |
mohs |
Characteristics |
Radioactive |
| Reaction with air |
|
Reaction with 6M HCl |
|
| Reaction with 6M HCl |
|
Reaction with 15M HNO3 |
|
| Reaction with 6M NaOH |
|
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| Number of isotopes |
0 |
Hydride(s) |
|
| Oxide(s) |
CfO Cf2O3 CfO2 |
Chloride(s) |
CfCl3 |
| Ionic radius (2- ion) |
pm |
Ionic radius (1- ion) |
pm |
| Atomic radius |
186 pm |
Ionic radius (1+ ion) |
pm |
| Ionic radius (2+ ion) |
pm |
Ionic radius (3+ ion) |
109 pm |
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| Thermal conductivity |
J/m-sec-deg |
Electrical conductivity |
1/mohm-cm |
| Polarizability |
20.5 A^3 |
| Source |
Synthetic |
Rel. abund. solar system |
log |
| Abundance earth's crust |
log |
Cost, pure |
$/100g |
| Cost, bulk |
$/100g |
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History:
(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 gages 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. 252-Cf
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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