FERMIUM

introduction

Numéro atomique: 100
Groupe: Aucun
Poids atomique: 257
Période: 7
Numero CAS: 7440-72-4

Classification

chalcogènes
Halogène
Gaz rare
lanthanides
actinides
Rare Earth Element
Groupe Platine Métal
Transuranium
Pas d'isotopes stables
Solide
Liquide
Gaz
Solide (prédit)

La description • Usages / Fonction

Fermium, the eighth transuranium element of the actinide series to be discovered, was identified by Ghiorso and co-workers in 1952 in the debris from a thermonuclear explosion in the Pacific in work involving the University of California Radiation Laboratory, the Argonne National Laboratory, and the Los Alamos Scientific Laboratory. The isotope produced was the 20-hour 255Fm. During 1953 and early 1954, while discovery of elements 99 and 100 was withheld from publication for security reasons, a group from the Nobel Institute of Physics in Stockholm bombarded 238U with 16O ions, and isolated a 30-min a-emitter, which they ascribed to 250Fm, without claiming discovery of the element. This isotope has since been identified positively, and the 30-min half-life confirmed. The chemical properties of fermium have been studied solely with tracer amounts, and in normal aqueous media only the (III) oxidation state appears to exist. The isotope 254Fm and heavier isotopes can be produced by intense neutron irradiation of lower elements such as plutonium by a process of successive neutron capture interspersed with beta decays until these mass numbers and atomic numbers are reached. Twenty isotopes and isomers of fermium are known to exist. 257Fm, with a half-life of about 100.5 days, is the longest lived. 250Fm, with a half-life of 30 min, has been shown to be a product of decay of Element 254No. It was by chemical identification of 250Fm that production of nobelium was confirmed. 1

Propriétés physiques

Point de fusion:2*  1527 °C = 1800.15 K = 2780.6 °F
Point d'ébullition:2
sublimation point:2 
Triple point:2 
Point critique:2 
Densité:   g/cm3

* - at 1 atm

Configuration de l'électron

Configuration de l'électron:  *[Rn] 7s2 5f12
Bloque: f
Plus haut niveau d'énergie occupés: 7
Électrons de valence: 2

Nombres quantiques:

n = 5
ℓ = 3
m = 1
ms = -½

Bonding

ionisation potentiel   eV 3  kJ/mol  
ionisation potentiel   eV 3  kJ/mol  
ionisation potentiel   eV 3  kJ/mol  
1 6.5    627.2

isotopes

Nuclide Masse 4 Demi vie 4 Spin nucléaire 4 Énergie de liaison
242Fm 242.07343(43)# 0.8(2) ms 0+ 1,809.82 MeV
243Fm 243.07435(23)# 210(60) ms [0.18(+8-4) s] 7/2-# 1,817.89 MeV
244Fm 244.07408(30)# 3.3(5) ms 0+ 1,825.96 MeV
245Fm 245.07539(30)# 4.2(13) s 1/2+# 1,834.03 MeV
246Fm 246.07530(4) 1.1(2) s 0+ 1,842.10 MeV
247Fm 247.07685(15)# 29(1) s (7/2+) 1,850.17 MeV
248Fm 248.077195(13) 36(2) s 0+ 1,858.24 MeV
249Fm 249.07903(11)# 2.6(7) min (7/2+)# 1,866.32 MeV
250Fm 250.079521(13) 30(3) min 0+ 1,874.39 MeV
251Fm 251.081575(9) 5.30(8) h (9/2-) 1,873.14 MeV
252Fm 252.082467(6) 25.39(4) h 0+ 1,881.21 MeV
253Fm 253.085185(4) 3.00(12) d (1/2)+ 1,889.29 MeV
254Fm 254.0868542(30) 3.240(2) h 0+ 1,897.36 MeV
255Fm 255.089962(5) 20.07(7) h 7/2+ 1,905.43 MeV
256Fm 256.091773(8) 157.6(13) min 0+ 1,904.19 MeV
257Fm 257.095105(7) 100.5(2) d (9/2+) 1,912.26 MeV
258Fm 258.09708(22)# 370(14) μs 0+ 1,920.33 MeV
259Fm 259.1006(3)# 1.5(3) s 3/2+# 1,919.08 MeV
260Fm 260.10268(54)# 1# min 0+ 1,927.16 MeV
Les valeurs marquées # ne sont pas purement dérivées des données expérimentales, mais au moins en partie des tendances systématiques. Spins avec de faibles arguments d'affectation sont entre parenthèses. 4

Abondance

Information de sécurité


Fiche signalétique - ACI Alloys, Inc.

Pour plus d'informations

Liens externes:

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:12.
(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, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(7) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).