Introducción
Grupo: Ninguna
Peso atomico: 251
Período: 7
Número CAS: 7440-71-3
Clasificación
No hay isótopos estables
Sólido
Líquido
Gas
Sólido (Predicho)
Descripción • Usos / Función
Californium, the sixth transuranium element to be discovered, was produced by Thompson, Street, Ghioirso, and Seaborg in 1950 by bombarding microgram quantities of curium-242 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 californium-249 results from the beta decay of berkelium-249 while the heavier isotopes are produced by intense neutron irradiation by the reactions. Berkelium-249 is bombarded with a neutron to produce berkelium-250 which subsequently yields californium-250 via beta decay. Additionally, californium-249 can be bombarded with a neutron to yield californium-250. This can be followed by two successive neutron bomabrdments to yield californium-251 and californium-252. The existence of the isotopes californium-249, californium-250, californium-251, and californium-252 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. Eighteen isotopes of californium are now recognized. californium-249 and californium-252 have half-lives of 351 years and 900 years, respectively. In 1960 a few tenths of a microgram of californium trichloride, CfCl3, californium oxychloride, CfOCl, and californium oxide, Cf2O3, were first prepared. 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. Californium-252 is now being offered for sale by the Oak Ridge National Laboratory (O.R.N.L.) at a cost of $50/mg and californium-249 at a cost of $160/microgram plus packing charges. It has been suggested that californium may be produced in certain stellar explosions, called supernovae, for the radioactive decay of californium-254 (55-day half-life) agrees with the characteristics of the light curves of such explosions observed through telescopes. This suggestion, however, is questioned. 1
Propiedades físicas
Punto de fusion:2* 900 °C = 1173.15 K = 1652 °F
Configuración electronica: *[Rn] 7s2 5f10
n = 5
Calor especifico:
Enlaces externos:
(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:7.
Punto de ebullición:2*
Punto de sublimación:2
Triple punto:2
Punto crítico:2
Densidad:3 15.1 g/cm3
* - at 1 atm
Configuración electronica
Bloquear: f
Ocupado más alto nivel de energía: 7
Electrones de valencia: 2
Números cuánticos:
ℓ = 3
mℓ = -1
ms = -½
Vinculación
potencial de ionización
eV 4
kJ/mol
potencial de ionización
eV 4
kJ/mol
potencial de ionización
eV 4
kJ/mol
1
6.2817
606.1
termoquímica
Conductividad térmica: 10 (W/m)/K, 27°C 5
Calor de fusión:
Calor de vaporización:
Estado de la materia
Entalpía de formación (ΔHf°)6
entropía (S°)6
Energía libre de Gibbs (ΔGf°)6
(kcal/mol)
(kJ/mol)
(cal/K)
(J/K)
(kcal/mol)
(kJ/mol)
(g)
61
255.224
50.89
212.92376
53
221.752
isótopos
nucleido
Masa 7
Media vida 7
spin nuclear 7
Energía de unión
237Cf
237.06207(54)#
2.1(3) s
5/2+#
1,780.34 MeV
238Cf
238.06141(43)#
21.1(13) ms
0+
1,788.41 MeV
239Cf
239.06242(23)#
60(30) s [39(+37-12) s]
5/2+#
1,796.48 MeV
240Cf
240.06230(22)#
1.06(15) min
0+
1,804.55 MeV
241Cf
241.06373(27)#
3.78(70) min
7/2-#
1,812.63 MeV
242Cf
242.06370(4)
3.49(15) min
0+
1,820.70 MeV
243Cf
243.06543(15)#
10.7(5) min
(1/2+)
1,828.77 MeV
244Cf
244.066001(3)
19.4(6) min
0+
1,836.84 MeV
245Cf
245.068049(3)
45.0(15) min
(5/2+)
1,844.91 MeV
246Cf
246.0688053(22)
35.7(5) h
0+
1,852.98 MeV
247Cf
247.071001(9)
3.11(3) h
(7/2+)#
1,851.74 MeV
248Cf
248.072185(6)
333.5(28) d
0+
1,859.81 MeV
249Cf
249.0748535(24)
351(2) a
9/2-
1,867.88 MeV
250Cf
250.0764061(22)
13.08(9) a
0+
1,875.95 MeV
251Cf
251.079587(5)
900(40) a
1/2+
1,884.02 MeV
252Cf
252.081626(5)
2.645(8) a
0+
1,882.78 MeV
253Cf
253.085133(7)
17.81(8) d
(7/2+)
1,890.85 MeV
254Cf
254.087323(13)
60.5(2) d
0+
1,898.92 MeV
255Cf
255.09105(22)#
85(18) min
(7/2+)
1,897.68 MeV
256Cf
256.09344(32)#
12.3(12) min
0+
1,905.75 MeV
Los valores marcados con # no son puramente derivan de los datos experimentales, pero al menos en parte, de las tendencias sistemáticas. Hace girar con débiles argumentos de asignación se incluyen entre paréntesis. 7
Abundancia
Compuestos
Información de seguridad
Ficha de datos de seguridad de materiales - ACI Alloys, Inc.
Para más información
American Elements
Chemical & Engineering News
Chemical Elements
ChemGlobe
Chemicool
Environmental Chemistry
Fuentes
(2) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(8) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(9) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).