FERMIUM

introduzione

Numero atomico: 100
Gruppo: Nessuna
Peso atomico: 257
Periodo: 7
Numero CAS: 7440-72-4

Classificazione

Metallo
Metalloide
simile a metallo
metallo alcalino
Alkali terroso
Metallo di transizione
calcogeno
alogena
Gas nobile
Lanthanoid
Actinoid
Terre rare
Platinum Metal Group
transuranici
Non ci sono isotopi stabili
Solido
Liquido
Gas
Solido (previsto)

Descrizione • Usi / Funzione

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

Proprietà fisiche

Punto di fusione:2*  1527 °C = 1800.15 K = 2780.6 °F
Punto di ebollizione:2
sublimazione Point:2 
Triple Point:2 
Punto critico:2 
Densità:   g/cm3

* - at 1 atm

configurazione elettronica

configurazione elettronica:  *[Rn] 7s2 5f12
Bloccare: f
Più alto livello di energia Occupato: 7
Elettroni di valenza: 2

numeri quantici:

n = 5
ℓ = 3
m = 1
ms = -½

bonding

potenziale di ionizzazione   eV 3  kJ/mol  
potenziale di ionizzazione   eV 3  kJ/mol  
potenziale di ionizzazione   eV 3  kJ/mol  
1 6.5    627.2

isotopi

nuclide Massa 4 Metà vita 4 spin nucleare 4 Energia di legame
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
I valori assegnati # non sono puramente derivati ​​da dati sperimentali, ma almeno parzialmente da tendenze sistematiche. Gira con argomenti di assegnazione deboli sono racchiusi tra parentesi. 4

Abbondanza

Informazioni sulla sicurezza


Scheda di sicurezza - ACI Alloys, Inc.

Per maggiori informazioni

Link esterno:

fonti

(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).