Tungsten is a dense, silvery-gray transition metal with the highest melting point of all metals. It is used in hard alloys, electrical filaments, and high-temperature applications.
The electron configuration of tungsten is [Xe] 4f14 5d4 6s2. The partially filled 5d orbital contributes to its hardness, strength, and metallic bonding characteristics.
Tungsten has the strongest metallic bonding due to the overlap of its 5d and 6s electrons, leading to high cohesive energy. Its melting point is approximately 3422 °C, making it extremely resistant to heat and suitable for high-temperature environments like furnace filaments and rocket nozzles.
Major applications include:
Tungsten carbide (WC) is a compound formed by tungsten and carbon. It is one of the hardest known materials, used in cutting tools, mining machinery, and abrasives. Its formation reaction is represented as:
\(\mathrm{W(s) + C(s) \rightarrow WC(s)}\)
Tungsten’s exceptionally high melting point and low vapor pressure allow it to withstand the intense heat generated in bulbs without melting or evaporating quickly. Its high tensile strength also prevents filament breakage at elevated temperatures.
Tungsten commonly shows oxidation states from +2 to +6, with +6 being the most stable. For example, in tungsten trioxide (WO3), the oxidation state of W is +6. The variety of oxidation states makes tungsten versatile in catalysis and chemical reactions.
Tungsten is resistant to corrosion and oxidation at room temperature but forms oxides at high temperatures. When heated in oxygen, it forms tungsten(VI) oxide:
\(\mathrm{W(s) + 3\,O_2(g) \rightarrow 2\,WO_3(s)}\)
It also reacts with halogens to form halides like WF6 and WCl6.
Tungsten is a very dense (19.25 g/cm³), hard, and brittle metal with a silvery-gray luster. It has the highest melting point (3422 °C) and highest tensile strength of any pure metal. It also conducts electricity and heat efficiently.
Tungsten occurs mainly in minerals such as wolframite [(Fe,Mn)WO4] and scheelite (CaWO4). It is extracted by converting these ores into tungsten trioxide (WO3), which is then reduced with hydrogen:
\(\mathrm{WO_3(s) + 3\,H_2(g) \rightarrow W(s) + 3\,H_2O(g)}\)
Metallic tungsten is not toxic and is safe for industrial and consumer use. However, some tungsten compounds (like tungsten hexafluoride) are toxic or corrosive and must be handled with care. Inhalation of tungsten dust should be avoided to prevent respiratory irritation.
Tungsten reacts with fluorine gas to form tungsten hexafluoride, a volatile compound used in semiconductor manufacturing:
\(\mathrm{W(s) + 3\,F_2(g) \rightarrow WF_6(g)}\)
WF6 is a colorless gas used for chemical vapor deposition of tungsten films.