Chemistry

An Overview about the Chemical Element Tungsten



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Tungsten

Symbol: W

Atomic Number: 74

Atomic Mass: 183.84 amu (atomic mass units)

Melting Point: 3410.0 C (3683.15 K, 6170.0 F)

Boiling Point: 5660.0 C (5933.15 K, 10220.0 F)

Number of Protons: 74

Number of Electrons: 74

Number of Neutrons: 110

Classification: Transition Metal

Crystal Structure: Cubic

Density @ 293 K: 19.3 grams per cubic centimeter

Color: Silver

Tungsten was discovered by the Spanish scientists and brothers Fausto and Juan-Jose de Elhuyar in 1783. Its name derives from the Swedish "tung sten" which means heavy stone. The symbol W is from the German name of the element "wolfram". It is commonly extracted from the mineral ore wolframite. Wolframite interferes with the smelting of tin and its name translates as devourer of tin.

The element has the highest melting point of any known metal. It is ductile and can be drawn out to form a wire. If contaminated with other metals tungsten becomes brittle and difficult to work. The pure metal can be cut using a hacksaw.

There are five naturally occurring isotopes of tungsten. In order of abundance these isotopes are tungsten-184 (30.64%), tungsten-186 (28.43%), tungsten-182 (26.5%), tungsten-183 (14.31%) and tungsten-180 (0.12%). All of the naturally occurring isotopes are unstable and have extremely long half-lives. Tungsten-183 decays by isomeric transition while the other four isotopes decay by alpha decay. Numerous other isotopes of tungsten have been made with mass numbers ranging from 158 to 190. Tunsten-158 has the shortest half-life of any of the known isotopes at 0.9 milliseconds and it decays by alpha decay.

Tungsten is extracted from the mineral ores wolframite and scheelite using methods similar to those devised by the de Elhuyar brothers. The ore is crushed before being treated with alkalis to yield tungsten trioxide. The tungsten trioxide is then heated with either hydrogen or carbon. This will produce pure tungsten metal and either water or carbon dioxide.

Many of the uses for tungsten are a result of its high melting point.

* It is used to make the filaments used in light bulbs and television sets.

* Tungsten is used in electric furnaces were it forms the heating element.

* It is used in microbiology laboratories to make the loops and straight wires used in bacterial culturing methods. It is able to withstand the repeated heating in a Bunsen flam that such methods require.

* As it has a similar thermal expansion rate as borosilicate glass tungsten is used to make metal to glass seals.

* The aerospace industry uses tungsten to form parts of space craft that may be subjected to extreme heat. It is also used in the production of missiles.

* Steel tungsten alloys are used to make the nozzles of rocket engines as well as cutting tools that are required to work at high temperatures.

* Tungsten carbide is a very hard compound that is used to make drill bits and mining equipment.

* The compound tungsten disulfide forms a dry lubricant. It works as a lubricant in temperatures as high as 500 C (773K 932F)

* Compounds of tungsten with magnesium and calcium exhibit phosphorescence. These compounds are used in the manufacture of fluorescent light tubes.

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