TUNGSTENO

Introducción

Número atómico: 74
Grupo: 6 or VI B
Peso atomico: 183.84
Período: 6
Número CAS: 7440-33-7

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

In 1779 Peter Woulfe examined the mineral now known as wolframite and concluded it must contain a newsubstance. Scheele, in 1781, found that a new acid could be made from tung sten (a name first applied about 1758 to a mineral now known as scheelite).Scheele and Berman suggested the possibility of obtaining a new metal by reducing this acid. The de Elhuyar brothers found an acid in wolframitein 1783 that was identical to the acid of tungsten (tungstic acid) of Scheele, and in that year they succeeded in obtaining the element by reduction ofthis acid with charcoal. Tungsten occurs in wolframite, (Fe, Mn)WO4; scheelite, CaWO4; huebnerite, MnWO4; and ferberite, FeWO4. Importantdeposits of tungsten occur in California, Colorado, South Korea, Bolivia, Russia, and Portugal. China is reported to have about 75% of the world’stungsten resources. Natural tungsten contains five stable isotopes. Thirty two other unstable isotopes and isomers are recognized. The metal is obtainedcommercially by reducing tungsten oxide with hydrogen or carbon. Pure tungsten is a steel-gray to tin-white metal. Very pure tungsten can be cut witha hacksaw, and can be forged, spun, drawn, and extruded. The impure metal is brittle and can be worked only with difficulty. Tungsten has the highestmelting point of all metals, and at temperatures over 1650°C has the highest tensile strength. The metal oxidizes in air and must be protected at elevatedtemperatures. It has excellent corrosion resistance and is attacked only slightly by most mineral acids. The thermal expansion is about the same asborosilicate glass, which makes the metal useful for glass-to-metal seals. Tungsten and its alloys are used extensively for filaments for electric lamps,electron and television tubes, and for metal evaporation work; for electrical contact points for automobile distributors; X-ray targets; windings andheating elements for electrical furnaces; and for numerous spacecraft and high-temperature applications. High-speed tool steels, Hastelloy(R), Stellite(R),and many other alloys contain tungsten. Tungsten carbide is of great importance to the metal-working, mining, and petroleum industries.Calcium andmagnesium tungstates are widely used in fluorescent lighting; other salts of tungsten are used in the chemical and tanning industries. Tungsten disulfideis a dry, high-temperature lubricant, stable to 500°C. Tungsten bronzes and other tungsten compounds are used in paints. Tungsten powder (99.95%)costs about $325/kg. 1

• "Wolfram has the highest melting point, 3370°C, of any of the metals. It is on this accoun that the wolfram filaments of light bulbs can be raised without melting to a temperature at which it emits an intense white light.

Wolfram is produced in the form of a gray powder. One of the earliest triumphs of powder metallurgy was the conversion of this powder in the electric furnace into an ingot which could be formed into a rod by hammering and then drawn through an electrically heated die into the exceedingly fine filament seen in our incandescent lamps. The atoms in this filament have arranged themselves in a crystal lattice structure.

Wolfram is used as a substitute for platinum in electric contact points and terminals for spark gaps, also for wiring electric furnaces and as targets for X-ray tubes. It is an important constituent of alloy steels." 2
• "A number of transition metals (Ti, Zr, Hf, V, Nb, Ta, Mo, W) form interstitial carbides of composition MC and, in some cases, M2C. These carbides have extremely high melting points; they are very hard, and they are good electrical conductors." 3

Propiedades físicas

Punto de fusion:4*  3422 °C = 3695.15 K = 6191.6 °F
Punto de ebullición:4* 5555 °C = 5828.15 K = 10031 °F
Punto de sublimación:4 
Triple punto:4 
Punto crítico:4 
Densidad:5  19.3 g/cm3

* - at 1 atm

Configuración electronica

Configuración electronica: [Xe] 6s2 4f14 5d4
Bloquear: d
Ocupado más alto nivel de energía: 6
Electrones de valencia: 

Números cuánticos:

n = 5
ℓ = 2
m = 1
ms = +½

Vinculación

electronegatividad (escala de Pauling):6 1.7
Electropositivity (escala de Pauling): 2.3
Afinidad electronica:7 0.815 eV
estados de oxidación: +6,4
Función del trabajo:8 4.55 eV = 7.2891E-19 J

potencial de ionización   eV 9  kJ/mol  
potencial de ionización   eV 9  kJ/mol  
potencial de ionización   eV 9  kJ/mol  
1 7.864    758.8

termoquímica

Calor especifico: 0.132 J/g°C 10 = 24.267 J/mol°C = 0.032 cal/g°C = 5.800 cal/mol°C
Conductividad térmica: 174 (W/m)/K, 27°C 11
Calor de fusión: 35.4 kJ/mol 12 = 192.6 J/g
Calor de vaporización: 824 kJ/mol 13 = 4482.2 J/g
Estado de la materia Entalpía de formación (ΔHf°)14 entropía (S°)14 Energía libre de Gibbs (ΔGf°)14
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 7.81 32.67704 0 0
(ℓ) 11.22 46.94448 10.92 45.68928 9.66 40.41744
(g) 203.4 851.0256 41.55 173.8452 193.3 808.7672

isótopos

nucleido Masa 15 Media vida 15 spin nuclear 15 Energía de unión
158W 157.97456(54)# 1.37(17) ms 0+ 1,245.32 MeV
159W 158.97292(43)# 8.2(7) ms 7/2-# 1,253.39 MeV
160W 159.96848(22) 90(5) ms 0+ 1,270.77 MeV
161W 160.96736(21)# 409(16) ms 7/2-# 1,278.85 MeV
162W 161.963497(19) 1.36(7) s 0+ 1,286.92 MeV
163W 162.96252(6) 2.8(2) s 3/2-# 1,294.99 MeV
164W 163.958954(13) 6.3(2) s 0+ 1,312.37 MeV
165W 164.958280(27) 5.1(5) s 3/2-# 1,320.45 MeV
166W 165.955027(11) 19.2(6) s 0+ 1,328.52 MeV
167W 166.954816(21) 19.9(5) s 3/2-# 1,336.59 MeV
168W 167.951808(17) 51(2) s 0+ 1,344.66 MeV
169W 168.951779(17) 76(6) s (5/2-) 1,352.73 MeV
170W 169.949228(16) 2.42(4) min 0+ 1,370.12 MeV
171W 170.94945(3) 2.38(4) min (5/2-) 1,378.19 MeV
172W 171.94729(3) 6.6(9) min 0+ 1,386.26 MeV
173W 172.94769(3) 7.6(2) min 5/2- 1,394.33 MeV
174W 173.94608(3) 33.2(21) min 0+ 1,402.40 MeV
175W 174.94672(3) 35.2(6) min (1/2-) 1,410.47 MeV
176W 175.94563(3) 2.5(1) h 0+ 1,418.55 MeV
177W 176.94664(3) 132(2) min 1/2- 1,426.62 MeV
178W 177.945876(16) 21.6(3) d 0+ 1,434.69 MeV
179W 178.947070(17) 37.05(16) min (7/2)- 1,442.76 MeV
180W 179.946704(4) ESTABLE 0+ 1,450.83 MeV
181W 180.948197(5) 121.2(2) d 9/2+ 1,458.90 MeV
182W 181.9482042(9) ESTABLE 0+ 1,466.97 MeV
183W 182.9502230(9) ESTABLE 1/2- 1,465.73 MeV
184W 183.9509312(9) ESTABLE 0+ 1,473.80 MeV
185W 184.9534193(10) 75.1(3) d 3/2- 1,481.87 MeV
186W 185.9543641(19) ESTABLE 0+ 1,489.94 MeV
187W 186.9571605(19) 23.72(6) h 3/2- 1,498.02 MeV
188W 187.958489(4) 69.78(5) d 0+ 1,506.09 MeV
189W 188.96191(21) 11.6(3) min (3/2-) 1,504.84 MeV
190W 189.96318(18) 30.0(15) min 0+ 1,512.91 MeV
191W 190.96660(21)# 20# s [>300 ns] 3/2-# 1,520.99 MeV
192W 191.96817(64)# 10# s [>300 ns] 0+ 1,529.06 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. 15

Abundancia

Tierra - Los compuestos de origen: oxides 16
Tierra - Agua de mar: 0.0001 mg/L 17
Tierra -  Corteza:  1.25 mg/kg = 0.000125% 17
Tierra -  Total:  180 ppb 18
Planeta mercurio) -  Total:  139 ppb 18
Venus -  Total:  189 ppb 18
condritas - Total: 0.12 (relative to 106 atoms of Si) 19

Compuestos

Información de seguridad


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

Para más información

Enlaces externos:

revistas:
(1) Gumbsch, Riedle, Hartmaier and Fischmeister, Science 282, 1293-1295 (1998)
(2) John Trowbridge and Samuel Sheldon, Proc. Am. Acad. Arts Sci. 24, 181-184 (1889)

Fuentes

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:33.
(2) - Brownlee, Raymond B., Fuller, Robert W., and Whitsit, Jesse E. Elements of Chemistry; Allyn and Bacon: Boston, Massachusetts, 1959; pp 560-1.
(3) - Jolly, William L. The Chemistry of the Non-Metals; Prentice-Hall: Englewood Cliffs, New Jersey, 1966; p 119.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 4:39-4:96.
(6) - Dean, John A. Lange's Handbook of Chemistry, 11th ed.; McGraw-Hill Book Company: New York, NY, 1973; p 4:8-4:149.
(7) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(8) - Speight, James. Lange's Handbook of Chemistry, 16th ed.; McGraw-Hill Professional: Boston, MA, 2004; p 1:132.
(9) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 10:178 - 10:180.
(10) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:133.
(11) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(12) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(13) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(14) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(15) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).
(16) - Silberberg, Martin S. Chemistry: The Molecular Nature of Matter and Change, 4th ed.; McGraw-Hill Higher Education: Boston, MA, 2006, p 965.
(17) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 14:17.
(18) - Morgan, John W. and Anders, Edward, Proc. Natl. Acad. Sci. USA 77, 6973-6977 (1980)
(19) - Brownlow, Arthur. Geochemistry; Prentice-Hall, Inc.: Englewood Cliffs, NJ, 1979, pp 15-16.