Tungsten is a chemical element with the symbol W (Wolfram in Latin) and atomic number 74. It is a hard, rare metal which is found naturally only in chemical compounds. Tungsten is used as a contact material in reed switches due to its resistance to damage by arcing, but is not be used in applications where low Contact Resistance is required.
Tungsten, or wolfram, 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.
|Alternative name||wolfram, pronounced: // (WUUL-frəm)|
|Allotropes||α-tungsten (common), β-tungsten|
|Appearance||grayish white, lustrous|
|Standard atomic weight Ar°(W)|
|Tungsten in the periodic table|
|Atomic number (Z)||74|
|Electron configuration||[Xe] 4f14 5d4 6s2|
|Electrons per shell||2, 8, 18, 32, 12, 2|
|Phase at STP||solid|
|Melting point||3695 K (3422 °C, 6192 °F)|
|Boiling point||6203 K (5930 °C, 10706 °F)|
|Density (near r.t.)||19.25 g/cm3|
|when liquid (at m.p.)||17.6 g/cm3|
|Heat of fusion||52.31 kJ/mol|
|Heat of vaporization||774 kJ/mol|
|Molar heat capacity||24.27 J/(mol·K)|
|Oxidation states||−4, −2, −1, 0, +1, +2, +3, +4, +5, +6 (a mildly acidic oxide)|
|Electronegativity||Pauling scale: 2.36|
|Atomic radius||empirical: 139 pm|
|Covalent radius||162±7 pm|
|Spectral lines of tungsten|
|Crystal structure||body-centered cubic (bcc)|
|Speed of sound thin rod||4620 m/s (at r.t.) (annealed)|
|Thermal expansion||4.5 µm/(m⋅K) (at 25 °C)|
|Thermal conductivity||173 W/(m⋅K)|
|Electrical resistivity||52.8 nΩ⋅m (at 20 °C)|
|Molar magnetic susceptibility||+59.0×10−6 cm3/mol (298 K)|
|Young's modulus||411 GPa|
|Shear modulus||161 GPa|
|Bulk modulus||310 GPa|
|Vickers hardness||3430–4600 MPa|
|Brinell hardness||2000–4000 MPa|
|Discovery and first isolation||Juan José Elhuyar and Fausto Elhuyar (1783)|
|Named by||Torbern Bergman (1781)|
|Symbol||"W": from Wolfram, originally from Middle High German wolf-rahm 'wolf's foam' describing the mineral wolframite|
|Main isotopes of tungsten|
The free element is remarkable for its robustness, especially the fact that it has the highest melting point of all known elements barring carbon (which sublimes at normal pressure), melting at 3,410 °C (6,170 °F; 3,683 K). It also has the highest boiling point, at 5,930 °C (10,706 °F; 6,203 K). Its density is 19.30 grams per cubic centimetre (0.697 lb/cu in), comparable with that of uranium and gold, and much higher (about 1.7 times) than that of lead. Polycrystalline tungsten is an intrinsically brittle 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.
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.