The chemical element tungsten is classed as a transition metal. It was discovered in 1779 by Peter Woulfe.
|Classification:||Tungsten is a transition metal|
|Melting point:||3422 oC, 3695 K|
|Boiling point:||5550 oC, 5823 K|
|Neutrons in most abundant isotope:||110|
|Electron configuration:||[Xe] 4f14 5d4 6s2|
|Density @ 20oC:||19.3 g/cm3|
|Atomic volume:||9.53 cm3/mol|
|Structure:||bcc: body-centered cubic|
|Specific heat capacity||0.13 J g-1 K-1|
|Heat of fusion||35.40 kJ mol-1|
|Heat of atomization||860 kJ mol-1|
|Heat of vaporization||824.0 kJ mol-1|
|1st ionization energy||770 kJ mol-1|
|2nd ionization energy||1700 kJ mol-1|
|3rd ionization energy||–|
|Electron affinity||78.6 kJ mol-1|
|Minimum oxidation number||-2|
|Min. common oxidation no.||0|
|Maximum oxidation number||6|
|Max. common oxidation no.||6|
|Electronegativity (Pauling Scale)||2.36|
|Polarizability volume||11.1 Å3|
|Reaction with air||w/ht, ⇒ WO3|
|Reaction with 15 M HNO3||none|
|Reaction with 6 M HCl||none|
|Reaction with 6 M NaOH||–|
|Oxide(s)||WO2, WO3 (tungstic oxide)|
|Chloride(s)||WCl2, WCl4, WCl6|
|Atomic radius||139 pm|
|Ionic radius (1+ ion)||–|
|Ionic radius (2+ ion)||–|
|Ionic radius (3+ ion)||–|
|Ionic radius (1- ion)||–|
|Ionic radius (2- ion)||–|
|Ionic radius (3- ion)||–|
|Thermal conductivity||173 W m-1 K-1|
|Electrical conductivity||18.2 x 106 S m-1|
|Freezing/Melting point:||3422 oC, 3695 K|
Discovery of Tungsten
In 1779 Irish chemist Peter Woulfe deduced the existence of a new element – tungsten – from his analysis of the mineral wolframite (an iron manganese tungstate mineral).
Tungsten was isolated as tungstic oxide (WO3) in 1781, in Sweden, by Carl W. Scheele from the mineral scheelite (calcium tungstate). However he did not have a suitable furnace to reduce the oxide to the metal.
Tungsten was finally isolated by brothers Fausto and Juan Jose de Elhuyar in 1783, in Spain, by reduction of acidified wolframite with charcoal.
The element name comes from the Swedish words ‘tung sten’ meaning heavy stone.
The chemical symbol, W, comes from the original name of the element, Wolfram.
Appearance and Characteristics
Tungsten is considered to be of low toxicity.
Tungsten is a very hard, dense, silvery-white, lustrous metal that tarnishes in air, forming a protective oxide coating. In powder form tungsten is gray.
The metal has the highest melting point of all metals, and at temperatures over 1650 oC also has the highest tensile strength. Pure tungsten is ductile, and tungsten wires, even of a very small diameter, have a very high tensile strength.
Tungsten is highly resistant to corrosion. It forms tungstic acid (H2WO4), or wolframic acid from the hydrated oxide (WO3) and its salts are called tungstates, or wolframates.
When present in compounds, tungsten exists mostly in the oxidation state VI.
Tungsten is one of the five major refractory metals (metals with very high resistance to heat and wear).
The Five Refractory Metals – note their close relationship in the periodic table
Uses of Tungsten
Tungsten and its alloys are widely used for filaments in older style (not energy saving) electric bulbs and electronic tubes.
Tungsten is also used as the filament in halogen tungsten lamps. These lamps use halogens like bromine and iodine to prevent the tungsten filament from degrading and are therefore more energy efficient than standard incandescent light bulbs.
High speed steel (which can cut material at higher speeds than carbon steel), contains up to 18% tungsten.
Tungsten is used in heavy metal alloys because of its hardness and in high-temperature applications such as welding.
Abundance and Isotopes
Abundance earth’s crust: 1.25 parts per million by weight, 0.1 parts per million by moles
Abundance solar system: 4 parts per billion by weight, 30 part per trillion by moles
Cost, pure: $11 per 100g
Cost, bulk: $2.95 per 100g
Source: Tungsten is not found free in nature. The principal ores of tungsten are wolframite (an iron manganese tungstate) and scheelite (calcium tungstate, CaWO3). Commercially, the metal is obtained by reducing tungsten oxide with hydrogen or carbon.
Isotopes: Tungsten has 33 isotopes whose half-lives are known with mass numbers from 158 to 190. Naturally occurring tungsten is a mixture of five isotopes and they are found in the percentages shown: 180W (0.1%), 182W (26.5%), 183W (14.3%), 184W (30.6%) and 186W (28.4%).
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