Tungsten

Tungsten, or wolfram,[9][10] is a chemical element with the symbol W and atomic number 74. Tungsten is a rare metal found naturally on Earth almost exclusively as compounds with other elements. It was identified as a new element in 1781 and first isolated as a metal in 1783. Its important ores include scheelite, and wolframite, the latter lending the element its alternate name.

Tungsten, 74W
Tungsten
Pronunciation/ˈtʌŋstən/ (TUNG-stən)
Alternative namewolfram, pronounced: /ˈwʊlfrəm/ (WUUL-frəm)
Appearancegrayish white, lustrous
Standard atomic weight Ar, std(W)183.84(1)[1]
Tungsten in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson
Mo

W

Sg
tantalumtungstenrhenium
Atomic number (Z)74
Groupgroup 6
Periodperiod 6
Block  d-block
Electron configuration[Xe] 4f14 5d4 6s2[2]
Electrons per shell2, 8, 18, 32, 12, 2
Physical properties
Phase at STPsolid
Melting point3695 K (3422 °C, 6192 °F)
Boiling point6203 K (5930 °C, 10706 °F)
Density (near r.t.)19.3 g/cm3
when liquid (at m.p.)17.6 g/cm3
Heat of fusion52.31 kJ/mol[3][4]
Heat of vaporization774 kJ/mol
Molar heat capacity24.27 J/(mol·K)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 3477 3773 4137 4579 5127 5823
Atomic properties
Oxidation states−4, −2, −1, 0, +1, +2, +3, +4, +5, +6 (a mildly acidic oxide)
ElectronegativityPauling scale: 2.36
Ionization energies
  • 1st: 770 kJ/mol
  • 2nd: 1700 kJ/mol
Atomic radiusempirical: 139 pm
Covalent radius162±7 pm
Color lines in a spectral range
Spectral lines of tungsten
Other properties
Natural occurrenceprimordial
Crystal structure body-centered cubic (bcc)
Speed of sound thin rod4620 m/s (at r.t.) (annealed)
Thermal expansion4.5 µm/(m⋅K) (at 25 °C)
Thermal conductivity173 W/(m⋅K)
Electrical resistivity52.8 nΩ⋅m (at 20 °C)
Magnetic orderingparamagnetic[5]
Molar magnetic susceptibility+59.0×10−6 cm3/mol (298 K)[6]
Young's modulus411 GPa
Shear modulus161 GPa
Bulk modulus310 GPa
Poisson ratio0.28
Mohs hardness7.5
Vickers hardness3430–4600 MPa
Brinell hardness2000–4000 MPa
CAS Number7440-33-7
History
Discovery and first isolationJuan José Elhuyar and Fausto Elhuyar[7] (1783)
Named byTorbern Bergman (1781)
Symbol"W": from Wolfram, originally from Middle High German wolf-rahm 'wolf's foam' describing the mineral wolframite[8]
Main isotopes of tungsten
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
180W 0.12% 1.8×1018 y α 176Hf
181W syn 121.2 d ε 181Ta
182W 26.50% stable
183W 14.31% stable
184W 30.64% stable
185W syn 75.1 d β 185Re
186W 28.43% stable
 Category: Tungsten
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The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all the elements discovered except carbon (which sublimes at normal pressure), melting at 3,422 °C (6,192 °F; 3,695 K). It also has the highest boiling point, at 5,930 °C (10,710 °F; 6,200 K).[11] Its density is 19.25 grams per cubic centimetre,[12] comparable with that of uranium and gold, and much higher (about 1.7 times) than that of lead.[13] Polycrystalline tungsten is an intrinsically brittle[14][15] and hard material (under standard conditions, when uncombined), making it difficult to work. However, pure single-crystalline tungsten is more ductile and can be cut with a hard-steel hacksaw.[16]

Tungsten occurs in many alloys, which have numerous applications, including incandescent light bulb filaments, X-ray tubes, electrodes in gas tungsten arc welding, superalloys, and radiation shielding. Tungsten's hardness and high density make it suitable for military applications in penetrating projectiles. Tungsten compounds are often used as industrial catalysts.

Tungsten is the only metal in the third transition series that is known to occur in biomolecules, being found in a few species of bacteria and archaea. However, tungsten interferes with molybdenum and copper metabolism and is somewhat toxic to most forms of animal life.[17][18]