NEPTUNIUM

introduction

Numéro atomique: 93
Groupe: Aucun
Poids atomique: 237
Période: 7
Numero CAS: 7439-99-8

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

Neptuniumwas the first synthetic transuranium element of the actinide series discovered; the isotope neptunium-239 was produced by McMillan and Abelson in 1940 atBerkeley, California, as the result of bombarding uranium with cyclotron-produced neutrons. The isotope neptunium-237 (half-life of 2.14 X 10^6 years) iscurrently obtained in gram quantities as a by-product from nuclear reactors in the production of plutonium. Twenty isotopes and isomers of neptuniumare now recognized. Trace quantities of the element are actually found in nature due to transmutation reactions in uranium ores produced by the neutronswhich are present. Neptunium is prepared by the reduction of Npf3 with barium or lithium vapor at about 1200°C. Neptunium metal has a silveryappearance, is chemically reactive, and exists in at least three structural modifications: a-neptunium, orthorhombic, density 20.25 g/cm^3, beta-neptunium(above 280°C), tetragonal, density (313°C) 19.36 g/cm^3; g-neptunium (above 577°C), cubic, density (600°C) 18.0 g/cm^3. Neptunium has four ionicoxidation states in solution: Np+3 (pale purple), analogous to the rare earth ion Pm+3, Np+4 (yellow green); NpO+ (green blue); and NpO++ (pale pink).These latter oxygenated species are in contrast to the rare earths which exhibit only simple ions of the (II), (III), and (IV) oxidation states in aqueoussolution. The element forms tri- and tetrahalides such as Npf3, Npf4, NpCl4, NpBr3, NpI3, and oxides of various compositions such as are found inthe uranium-oxygen system, including Np3O8 and NpO2. Fifteen isotopes of neptunium are now recognized. The O.R.N.L. has neptunium-237 available for saleto its licensees and for export. This isotope can be used as a component in neutron detection instruments. It is offered at a price of $660/g plus packingcosts. 1

Propriétés physiques

Point de fusion:2*  644 °C = 917.15 K = 1191.2 °F
Point d'ébullition:2
sublimation point:2 
Triple point:2 
Point critique:2 
Densité:3  20.2 g/cm3

* - at 1 atm

Configuration de l'électron

Configuration de l'électron:  *[Rn] 7s2 5f5
Bloque: f
Plus haut niveau d'énergie occupés: 7
Électrons de valence: 2

Nombres quantiques:

n = 5
ℓ = 3
m = 1
ms = +½

Bonding

Électronégativité (échelle de Pauling):4 1.3
Electropositivity (échelle de Pauling): 2.7

ionisation potentiel   eV 5  kJ/mol  
ionisation potentiel   eV 5  kJ/mol  
ionisation potentiel   eV 5  kJ/mol  
1 6.2657    604.5

isotopes

Nuclide Masse 6 Demi vie 6 Spin nucléaire 6 Énergie de liaison
225Np 225.03391(8) 3# ms [>2 μs] 9/2-# 1,715.34 MeV
226Np 226.03515(10)# 35(10) ms 1,723.41 MeV
227Np 227.03496(8) 510(60) ms 5/2-# 1,731.48 MeV
228Np 228.03618(21)# 61.4(14) s 1,739.55 MeV
229Np 229.03626(9) 4.0(2) min 5/2+# 1,747.63 MeV
230Np 230.03783(6) 4.6(3) min 1,755.70 MeV
231Np 231.03825(5) 48.8(2) min (5/2)(+#) 1,763.77 MeV
232Np 232.04011(11)# 14.7(3) min (4+) 1,762.52 MeV
233Np 233.04074(5) 36.2(1) min (5/2+) 1,770.60 MeV
234Np 234.042895(9) 4.4(1) d (0+) 1,778.67 MeV
235Np 235.0440633(21) 396.1(12) d 5/2+ 1,786.74 MeV
236Np 236.04657(5) 154(6)E+3 a (6-) 1,794.81 MeV
237Np 237.0481734(20) 2.144(7)E+6 a 5/2+ 1,802.88 MeV
238Np 238.0509464(20) 2.117(2) d 2+ 1,801.64 MeV
239Np 239.0529390(22) 2.356(3) d 5/2+ 1,809.71 MeV
240Np 240.056162(16) 61.9(2) min (5+) 1,817.78 MeV
241Np 241.05825(8) 13.9(2) min (5/2+) 1,825.85 MeV
242Np 242.06164(21) 2.2(2) min (1+) 1,824.61 MeV
243Np 243.06428(3)# 1.85(15) min (5/2-) 1,832.68 MeV
244Np 244.06785(32)# 2.29(16) min (7-) 1,840.75 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. 6

Abondance

composés

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 4:20.
(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).