Stable isotopes of tungsten available from ISOFLEX
|Isotope||Z(p)||N(n)||Atomic Mass||Natural Abundance||Enrichment Level||Chemical Form|
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Tungsten was discovered in 1783 by Fausto and Juan José de Elhuyar. Its name derives from the Swedish phrase tung sten, meaning “heavy stone.” The origin of the symbol W is wolfram, named for the tungsten mineral wolframite.
Tungsten is a grayish-white metal with a body-centered cubic crystalline structure. It is not found in its native form. It has a high electrical conductivity. It oxidizes in air at 400° C, the oxidation rate increasing rapidly with temperature or in the presence of an oxidizing agent such as potassium nitrate, potassium chlorate or lead dioxide. It is insoluble in water and practically insoluble in most acids and alkalis. It dissolves slowly in hot concentrated nitric acid, in saturated aqueous solution of sodium chlorate and basic solution of potassium ferricyanide. It is also solubilized by fusion with sodium hydroxide or sodium carbonate in the presence of potassium nitrate, followed by treatment with water. It is soluble in a mixture of nitric acid and hydrofluoric acid and is corroded by seawater. Compounds of lower oxidation states show alkaline properties and are less stable than those produced in higher oxidation states. Tungsten metal is not affected by aqueous alkalis at room temperature. Although it exhibits a high degree of resistance to most chemicals, it is readily oxidized by a number of oxidizing agents. Tungsten reacts with oxygen at high temperatures, and the finely-divided powder is pyrophoric. It reacts with all halogens and with ammonia at elevated temperatures, forming tungstic nitrides and amides.
Tungsten forms a number of compounds with nonmetals and light metalloid elements. Many are important refractory materials in commerce. In industry, tungsten is a very important metal with wide applications, due to its many outstanding physical properties. Among all the metals, it has the highest melting point and the lowest vapor pressure. At high temperatures it also has the highest tensile strength. The metal has an excellent resistance to corrosion and attack by mineral acids, as well as a thermal expansion comparable to that of borosilicate glass. It is used extensively in alloy steel to impart high strength and hardness.
Heavy metal alloys with nickel, copper and iron, produced by powder metallurgy, can be made machineable and moderately ductile for applications as high-density materials. They are used extensively in the tool and die industry for drilling and cutting tools, sand-blasting nozzles, armor-piercing bullets, and studs to increase tire traction. Among nonferrous tungsten alloys, its alloys with copper and silver are used as electrical contacts and switches and with molybdenum in aerospace components. Unalloyed tungsten has several major applications: in electric lamp filaments for light bulbs, as electrodes in arc-welding, in heating elements for high-temperature furnaces, in electron and television tubes, in glass-to-metal seals and in solar energy devices. In its finely divided form, tungsten is highly flammable and may ignite spontaneously.
Properties of Tungsten
|Standard state||Solid at 298 ºK|
|CAS Registry ID||7440-33-7|
|Group in periodic table||6|
|Period in periodic table||6|
|Block in periodic table||d-block|
|Color||Grayish white, lustrous|
|Melting point||3422 °C|
|Boiling point||5900 °C|
|Vaporization point||5555 °C|
|Thermal conductivity||173 W/(m·K) at 298.2 °K|
|Electrical resistivity||5.65 µΩ·cm at 27 °C|
|Specific heat||0.13 kJ/kg K|
|Heat of vaporization||800 kJ·mol-1|
|Heat of fusion||35 kJ·mol-1|
|Density of liquid||17.6 g/cm3|
|Density of solid||19.3 g/cm3|
|Atomic radius||1.39 Å|
|Ionic radius||W4+: 0.66 Å and W5+: 0.62 Å (coordination number 6);
W6+: 0.42 Å (coordination number 4)
|Oxidation states||0, +2, +3, +4, +5, +6|
|Most stable oxidation state||+6|