74
  W  
183.840000
Tungsten

Name: Tungsten
Symbol: W
Atomic Number: 74
AtomicWeight: 183.840000
Family: Transition Metals
CAS RN: 7440-33-7
Description: A greyish white metal, very strong with the highest melting point of any metal.
State (25 C): Solid
Oxidation states: +6

Molar Volume: 9.5 cm3/mole
Valence Electrons: 5d46s2

Boiling Point:  5928K, 5655C, 10211F
Melting Point:
3680K, 3407C, 6165F
Electrons Energy Level: 2, 8, 18, 32, 12, 2
Isotopes: 30 + 5 Stable
Heat of Vaporization: 824 kJ/mol
Heat of Fusion: 35.4 kJ/mol
Density: 19.35 g/cm3 @ 300K
Specific Heat: 0.13 J/gK
Atomic Radius: 2.02
Ionic Radius: 0.62
Electronegativity: 2.36 (Pauling); 1.4 (Allrod Rochow)
Vapor Pressure: 4.27 Pa @ 3407C

1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d4 6s2

History

Tungsten (Swedish  tung sten meaning "heavy stone"), even though the current name for the element in Swedish is wolfram (sometimes spelled in Swedish as volfram), from the denomination volf rahm by Johan Gottschalk Wallerius in 1747, translated from the description by Georg Agricola in 1546 as Lupi spuma, meaning "wolf's froth" or "cream" after the way tin is eaten up like a wolf after sheep in the process of its extraction.

It was first hypothesized to exist by Peter Woulfe in 1779 who examined wolframite and concluded that it must contain a new substance.  In 1781 Carl Wilhelm Scheele ascertained that a new acid could be made from tungstenite.  Scheele and Torbern Bergman suggested that it could be possible to obtain a new metal by reducing tungstic acid.  Juan Jos and Fausto Elhuyar, Spanish chemists and brothers, in 1783 in samples of the mineral wolframite, (Fe, Mn)WO4 found an acid in wolframite that was identical to tungstic acid.  In Spain later that year the brothers succeeded in isolating tungsten through reduction of this acid with charcoal.  They are credited with the discovery of the element.

Tungsten ores are crushed, cleaned and treated with alkalis to form tungsten trioxide, WO3.  Tungsten trioxide is then heated with carbon or hydrogen gas, H2, forming tungsten metal and carbon dioxide, CO2, or tungsten metal and water vapor, H2O.

In World War II, tungsten played an enormous role in background political dealings.   Portugal, as the main European source of the element, was put under pressure from both sides, because of its sources of wolframite ore.  The resistance to high temperatures, as well as the extreme strength of its alloys, made the metal into a very important raw material for the weaponry industry.

Characteristics

Pure tungsten is steel-gray to tin-white and is a hard metal.  Tungsten can be cut with a hacksaw when it is very pure (it is brittle and hard to work when impure) and is otherwise worked by forging, drawing, extruding, or sintering.  This element has the highest melting point (3422C) (6192F), lowest vapor pressure and the highest tensil strength at temperatures above 1650C (3000F) of all metals.  Its corrosion resistance is excellent and it can only be attacked slightly by most mineral acids.   Tungsten metal forms a protective oxide when exposed to air but can be oxidized at high temperature.  Steel alloyed with small quantities of tungsten greatly increases its toughness.

1s2
2s2 2p6
3s2 3p6 3d10
4s2 4p6 4d10 4f14
5s2 5p6 5d4
6s2

Occurrence

Tungsten is found in the minerals wolframite (iron-manganese tungstate, FeWO4/MnWO4), scheelite (calcium tungstate, CaWO4), ferberite and hubnerite.  There are important deposits of these minerals in Bolivia, California, China, Colorado, Portugal, Russia, Vietnam and South Korea (with China producing about 75 % of the world's supply).  The metal is commercially produced by reducing tungsten oxide with hydrogen or carbon.

World tungsten reserves have been estimated at 7 million tons.  Unfortunately, most of these reserves are not economically workable so far.  At our current annual consumption rate, these reserves will only last for about 140 years.  China has been the largest supplier thus far.  According to further estimates, it has been suggested that 30% of the reserves are Wolframite and 70% are Scheelite ores.  Another factor that controls the tungsten supply is scrap recycling of tungsten and it has been proven to be a very valuable raw material in comparison to ore.

Applications

Tungsten is a metal with a wide range of uses, the largest of which is as tungsten carbide (W2C, WC) in cemented carbides.  Cemented carbides (also called hardmetals) are wear-resistant materials used by the metalworking, mining, petroleum and construction industries.  Tungsten is widely used in light bulb and vacuum tube filaments, as well as electrodes, because it can be drawn into very thin metal wires that have a high melting point.

Other uses:

Oxides are used in ceramic glazes and calcium/magnesium tungstates are used widely in fluorescent lighting.  Crystal tungstates are used as scintillation detectors in nuclear physics and nuclear medicine.  The metal is also used in X-ray targets and heating elements for electrical furnaces. Salts that contain tungsten are used in the chemical and tanning industries.  Tungsten 'bronzes' (so-called due to the colour of the tungsten oxides) along with other compounds are used in paints.  Tungsten Carbide has recently been used in the fashioning of jewelry due to its hypoallergenic nature and the fact that due to its extreme hardness it is not apt to lose its luster like other polished metals.  Some types of strings for musical instruments are wound with tungsten wire.

Compounds

The most common formal oxidation state of tungsten is +6, but it exhibits all oxidation states from -1 to +6.  Tungsten typically combines with oxygen to form the yellow tungstic oxide, WO3, which dissolves in aqueous alkaline solutions to form tungstate ions, WO42-.

Aqueous Polyoxoanions

Aqueous tungstate solutions are noted for the formation of polyoxoanions under neutral and acidic conditions.  As tungstate is progressively treated with acid, it first yields the soluble, metastable "paratungstate A" anion, W7O246-, which over hours or days converts to the less soluble "paratungstate B" anion, H2W12O4210-.   Further acidification produces the very soluble metatungstate anion, H2W12O406-, after equilibrium is reached.  The metatungstate ion exists as a symmetric cluster of twelve tungsten-oxygen octahedra known as the "Keggin" anion.  Many other polyoxoanions exist as metastable species.  The inclusion of a different atom such as phosphorus in place of the two central hydrogens in metatungstate produces a wide variety of the so-called heteropolyanions.

Isotopes

Naturally occurring tungsten consists of five isotopes whose half-lives are so long that they can be considered stable.  All can decay into isotopes of element 72 (hafnium) by alpha emission.  The other naturally occurring isotopes have not been observed to decay.  On average, two alpha decays of 180W occur in one gram of natural tungsten per year.

Thirty artificial radioisotopes of tungsten have been characterized, the most stable of which are 181W with a half-life of 121.2 days, 185W with a half-life of 75.1 days, 188W with a half-life of 69.4 days and 178W with a half-life of 21.6 days.  All of the remaining radioactive isotopes have half-lives of less than 24 hours, and most of these have half-lives that are less than 8 minutes.  Tungsten also has 4 meta states, the most stable being 179mW (t 6.4 minutes).

atom.gif (700 bytes)

Isotope  
Atomic Mass
 
Half-Life
158W ~157.97456 1.37 ms
159W ~158.97292 8.2 ms
160W 159.96848 90 ms
161W ~160.96736 409 ms
162W 161.963497 1.36 seconds
163W 162.96252 2.8 seconds
164W 163.958954 6.3 seconds
165W 164.958280 5.1 seconds
166W 165.955027 19.2 seconds
167W 166.954816 19.9 seconds
168W 167.951808 51 seconds
169W 168.951779 76 seconds
170W 169.949228 2.42 minutes
171W 170.94945 2.38 minutes
172W 171.94729 6.6 minutes
173W 172.94769 7.6 minutes
174W 173.94608 33.2 minutes
175W 174.94672 35.2 minutes
176W 175.94563 2.5 hours
177W 176.94664 132 minutes
178W 177.945876 21.6 days
179W 178.947070 37.05 minutes
180W 179.946704 Stable
181W 180.948197 121.2 days
182W 181.9482042 Stable
183W 182.9502230 Stable
184W 183.9509312 Stable
185W 184.9534193 75.1 days
186W 185.9543641 Stable
187W 186.9571605 23.72 hours
188W 187.958489 69.78 days
189W 188.96191 11.6 minutes
190W 189.96318 30.0 minutes
191W 190.96660 ~20 seconds
192W 191.96817 ~10 seconds

Precautions

40px-Skull_and_crossbones.svg.jpg (1420 bytes) On August 20, 2002, officials representing the Centers for Disease Control and Prevention announced that urine tests on leukemia patient families and control group families in the Fallon, Nevada area had shown elevated levels of the metal tungsten in the bodies of both groups. 

Sixteen recent cases of cancer in children were discovered in the Fallon area which has now been identified as a cancer cluster, (it should be noted, however, that the majority of the cancer victims are not long time residents of Fallon).  Dr. Carol H. Rubin, a branch chief at the CDC, said data demonstrating a link between tungsten and leukemia is not available at present.

atom.gif (700 bytes)

Tungsten Data
 

Atomic Structure

  • Atomic Radius: 2.02
  • Atomic Volume: 9.53cm3/mol
  • Covalent Radius: 1.3
  • Cross Section (Thermal Neutron Capture) Barns: 18.3
  • Crystal Structure: Cubic body centered
  • Electron Configuration:
    1s2 2s2p6 3s2p6d10 4s2p6d10f14 5s2p6d4 6s2
  • Electrons per Energy Level: 2, 8, 18, 32, 12, 2
  • Ionic Radius: 0.62
  • Filling Orbital: 5d4
  • Number of Electrons (with no charge): 74
  • Number of Neutrons (most common/stable nuclide): 110
  • Number of Protons: 74
  • Oxidation States: 6, 5, 4, 3, 2
  • Valence Electrons: 5d4 6s2

Chemical Properties

  • Electrochemical Equivalent: 1.1432 g/amp-hr
  • Electron Work Function: 4.55eV
  • Electronegativity: 2.36 (Pauling); 1.4 (Allrod Rochow)
  • Heat of Fusion: 35.4 kJ/mol
  • Incompatibilities:
    Bromine trifluoride, chlorine trifluoride, fluorine, iodine pentafluoride
  • Ionization Potential
    • First: 7.98
  • Valence Electron Potential (-eV): 140

Physical Properties

  • Atomic Mass Average: 183.85
  • Boiling Point: 5928K, 5655C, 10211F
  • Coefficient of Lineal Thermal Expansion/K-1: 4.59E-6
  • Conductivity
    Electrical: 0.189 106/cm
    Thermal: 1.74 W/cmK
  • Density: 19.35 g/cm3 @ 300K
  • Description:
    Hard, silver-white metal that is generally obtained as a dull grey powder that is hard to melt.
  • Elastic Modulus:
    • Bulk: 311/GPa
    • Rigidity: 160.5/GPa
    • Youngs: 411/GPa
  • Enthalpy of Atomization: 837 kJ/mole @ 25C
  • Enthalpy of Fusion: 35.23 kJ/mole
  • Enthalpy of Vaporization: 799.1 kJ/mole
  • Flammablity Class: Combustible
  • Freezing Point: see melting point
  • Hardness Scale
    • Brinell: 2570 MN m-2
    • Mohs: 7.5
    • Vickers: 3430 MN m-2
  • Heat of Vaporization: 824 kJ/mol
  • Melting Point: 3680K, 3407C, 6165F
  • Molar Volume: 9.5 cm3/mole
  • Optical Reflectivity: 62%
  • Physical State (at 20C & 1atm): Solid
  • Specific Heat: 0.13 J/gK
  • Vapor Pressure: 4.27 Pa @ 3407C

Regulatory / Health

  • CAS Number
    • 7440-33-7
  • RTECS: Y07175000
  • OSHA Permissible Exposure Limit (PEL)
    • No limits set by OSHA
  • OSHA PEL Vacated 1989
    • TWA: 5 mg/m3
    • STEL: 10 mg/m3
  • NIOSH Recommended Exposure Limit (REL)
    • TWA: 5 mg/m3
    • STEL: 10 mg/m3
  • Routes of Exposure: Inhalation; Ingestion; Skin and/or eye contact
  • Target Organs: Eyes, skin, respiratory system, blood
  • Levels In Humans:
    Note: this data represents naturally occuring levels of elements in the typical human, it DOES NOT represent recommended daily allowances.
    • Blood/mg dm-3: 0.001
    • Bone/p.p.m: 0.00025
    • Liver/p.p.m: n/a
    • Muscle/p.p.m: n/a
    • Daily Dietary Intake: 0.001-0.015 mg
    • Total Mass In Avg. 70kg human: 0.02 mg

Who / Where / When / How

  • Discoverer: Fausto and Juan Jos de Elhuijar
  • Discovery Location: Vergara Spain
  • Discovery Year: 1783
  • Name Origin:
    Swedish: tung sten (heavy stone): W symbol from its German name wolfram which is named after wolframite.
  • Abundance:
    • Earth's Crust/p.p.m.: 160.6
    • Seawater/p.p.m.: 0.000092
    • Atmosphere/p.p.m.: 411
    • Sun (Relative to H=1E12): 0.28
  • Sources:
    Occurs in the minerals scheelite (CaWO4) and wolframite [(Fe,Mn)WO4]. Annual world wide production is around 45,100 tons. Primary mining areas are China, Malaysia, Burma, bolivia, canada, Australia, Japan and USA.
  • Uses:
    Used widely in the electronics industry. Made into filaments for vacuum tubes and electric lights. Also used in contact points in cars, welding electrodes, rocket nozzles and cutting tools. Combined with calcium or magnesium it makes phosphors.
  • Additional Notes:
    Some sources give the German chemist Karl Wilhelm Scheele as the first to isolate the metal in 1880, but most sources credit the Elhuijar brothers.

Ionization Energy (eV): 7.98 eV
Estimated Crustal Abundance: 1.25 milligrams per kilogram
Estimated Oceanic Abundance:
110-4 milligrams per liter

Transition Metals
Group 3
(IIIB)
4
(IVB)
5
(VB)
6
(VIB)
7
(VIIB)
8
(VIIIB)
9
(VIIIB)
10 (VIIIB) 11
(IB)
12
(IIB)
Period 4 21
Sc
44.95
22
Ti
47.86
23
V
50.94
24
Cr
51.99
25
Mn
54.93
26
Fe
55.84
27
Co
58.93
28
Ni
58.69
29
Cu
63.54
30
Zn
65.39
Period 5 39
Y
88.90
40
Zr
91.22
41
Nb
92.90
42
Mo
95.94
43
Tc
98.00
44
Ru
101.0
45
Rh
102.9
46
Pd
106.4
47
Ag
107.8
48
Cd
112.4
Period 6 57
La
138.9
72
Hf
178.4
73
Ta
180.9
74
W
183.8
75
Re
186.2
76
Os
190.2
77
Ir
192.2
78
Pt
195.0
79
Au
196.9
80
Hg
200.5
Period 7 89
Ac
227.0
104
Rf
261.0
105
Db
262.0
106
Sg
266.0
107
Bh
264.0
108
Hs
269.0
109
Mt
268.0
110
Ds
269.0
111
Rg
272.0
112
Uub
277.0