CURIUM

Einführung

Ordnungszahl: 96
Gruppe: Keiner
Atomares Gewicht: 247
Periode: 7
CAS-Nummer: 7440-51-9

Einstufung

Metall
Nonmetal
metalloider
Alkalimetall
Erdalkalimetalls
Übergangsmetall
Chalkogenhaltige
Halogen
Edelgas
Lanthanoid
Actinoidenelemente
Seltene Erden
Platingruppenmetall
Transurane
Keine Stabile Isotope
Solide
Flüssigkeit
Gas
Solide (Prognostizierte)

Beschreibung • Verwendung / Funktion

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

Physikalische Eigenschaften

Schmelzpunkt:2*  1345 °C = 1618.15 K = 2453 °F
Siedepunkt:2* 3100 °C = 3373.15 K = 5612 °F
Sublimationspunkt:2 
Dreifacher Punkt:2 
Kritischer Punkt:2 
Dichte:3  13.51 g/cm3

* - at 1 atm

Elektronenkonfiguration

Elektronenkonfiguration:  *[Rn] 7s2 5f8
Block: f
Höchster besetztes Energieniveau: 7
Valenzelektronen: 2

Quantenzahlen:

n = 5
ℓ = 3
m = -3
ms = -½

Kleben

Ionisationspotential   eV 4  kJ/mol  
Ionisationspotential   eV 4  kJ/mol  
Ionisationspotential   eV 4  kJ/mol  
1 5.9915    578.1

Isotopes

Nuklid Masse 5 Halbwertzeit 5 Kernspin 5 Bindungsenergie
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
Werte markiert # sind nicht rein aus experimentellen Daten abgeleitet, aber zumindest teilweise von der systematischen Trends. Dreht mit schwachen Zuordnung Argumente in Klammern eingeschlossen sind. 5

Fülle

Verbindungen

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Datenblatt zur Materialsicherheit - ACI Alloys, Inc.

Für mehr Informationen

Externe Links:

Quellen

(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).