CURIO

Introducción

Número atómico: 96
Grupo: Ninguna
Peso atomico: 247
Período: 7
Número CAS: 7440-51-9

Clasificación

chalcogen
halógeno
Gas noble
Lantanoides
Actinoides
Elemento de tierras raras
Platino Metal Group
transuranium
No hay isótopos estables
Sólido
Líquido
Gas
Sólido (Predicho)

Descripción • Usos / Función

Although curium follows americium in the periodic system, it was actually known before americium and was the third transuranium element to be discovered. It was identified by Seaborg, James, and Ghiorso in 1944 at the wartime Metallurgical Laboratory in Chicago as a result of helium-ion bombardment of 239Pu in the Berkeley, California, 60-inch cyclotron. Visible amounts (30 micrograms) of 242Cm, in the form of the hydroxide, were first isolated by Werner and Perlman of the University of California in 1947. In 1950, Crane, Wallmann, and Cunningham found that the magnetic susceptibility of microgram samples of Cmf3 was of the same magnitude as that of Gdf3. This provided direct experimental evidence for assigning an electronic configuration to Cm+3. In 1951, the same workers prepared curium in its elemental form for the first time. Sixteen isotopes of curium are now known. The most stable, 247Cm, with a half-life of 16 million years, is so short compared to the earth’s age that any primordial curium must have disappeared long ago from the natural scene. Minute amounts of curium probably exist in natural deposits of uranium, as a result of a sequence of neutron captures and beta decays sustained by the very low flux of neutrons naturally present in uranium ores. The presence of natural curium, however, has never been detected. 242Cm and 244Cm are available in multigram quantities. 248Cm has been produced only in milligram amounts. Curium is similar in some regards to gadolinium, its rareearth homolog, but it has a more complex crystal structure. Curium is silver in color, is chemically reactive, and is more electropositive than aluminum. CmO2, Cm2O3, Cmf3, Cmf4, CmCl3, CmBr3, and CmI3 have been prepared. Most compounds of trivalent curium are faintly yellow in color. 242Cm generates about three watts of thermal energy per gram. This compares to one-half watt per gram of 238Pu. This suggests use for curium as a power source. 244Cm is now offered for sale at $160/mg plus packing charges. 248Cm is available at a cost of $160/microgram, plus packing charges, from the O.R.N.L. Curium absorbed into the body accumulates in the bones, and is therefore very toxic as its radiation destroys the red-cell forming mechanism. The maximum permissible total body burden of 244Cm (soluble) in a human being is 0.3 microcurie. 1

Propiedades físicas

Punto de fusion:2*  1345 °C = 1618.15 K = 2453 °F
Punto de ebullición:2* 3100 °C = 3373.15 K = 5612 °F
Punto de sublimación:2 
Triple punto:2 
Punto crítico:2 
Densidad:3  13.51 g/cm3

* - at 1 atm

Configuración electronica

Configuración electronica:  *[Rn] 7s2 5f8
Bloquear: f
Ocupado más alto nivel de energía: 7
Electrones de valencia: 2

Números cuánticos:

n = 5
ℓ = 3
m = -3
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 5.9915    578.1

isótopos

nucleido Masa 5 Media vida 5 spin nuclear 5 Energía de unión
232Cm 1? min 0+
233Cm 233.05077(8) 1# min 3/2+# 1,758.93 MeV
234Cm 234.05016(2) 51(12) s 0+ 1,767.01 MeV
235Cm 235.05143(22)# 5# min 5/2+# 1,775.08 MeV
236Cm 236.05141(22)# 10# min 0+ 1,783.15 MeV
237Cm 237.05290(22)# 20# min 5/2+# 1,791.22 MeV
238Cm 238.05303(4) 2.4(1) h 0+ 1,799.29 MeV
239Cm 239.05496(11)# ~2.9 h (7/2-) 1,807.36 MeV
240Cm 240.0555295(25) 27(1) d 0+ 1,815.43 MeV
241Cm 241.0576530(23) 32.8(2) d 1/2+ 1,823.50 MeV
242Cm 242.0588358(20) 162.8(2) d 0+ 1,831.58 MeV
243Cm 243.0613891(22) 29.1(1) a 5/2+ 1,830.33 MeV
244Cm 244.0627526(20) 18.10(2) a 0+ 1,838.40 MeV
245Cm 245.0654912(22) 8.5(1)E+3 a 7/2+ 1,846.48 MeV
246Cm 246.0672237(22) 4.76(4)E+3 a 0+ 1,854.55 MeV
247Cm 247.070354(5) 1.56(5)E+7 a 9/2- 1,853.30 MeV
248Cm 248.072349(5) 3.48(6)E+5 a 0+ 1,861.37 MeV
249Cm 249.075953(5) 64.15(3) min 1/2(+) 1,869.45 MeV
250Cm 250.078357(12) 8300# a 0+ 1,877.52 MeV
251Cm 251.082285(24) 16.8(2) min (1/2+) 1,876.27 MeV
252Cm 252.08487(32)# <1 d 0+ 1,884.34 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. 5

Abundancia

Compuestos

Información de seguridad


Ficha de datos de seguridad de materiales - ACI Alloys, Inc.

Para más información

Enlaces externos:

Fuentes

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:9-4:10.
(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) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(8) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(9) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).