English

Noun

metals

1. Plural of metal
2. the rail tracks owned by a company or organisation; a rail network

   It was appropriate that 'King' number 6000 began the return to steam on British Rail metals in 1971.

In chemistry, a metal (Greek: Metallon) is defined as an element that readily loses electrons to form positive ions (cations) and forms metallic bonds between other metal atoms (forming ionic bonds with non-metals).

Definition

The metals of the periodic table are formally defined as Lithium, beryllium, sodium, magnesium, aluminium, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, rubidium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, caesium, barium, lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, and bismuth.

Metals are good conductors, making them valuable in electrical appliances and for carrying an electric current over a distance with little energy lost. Electrical power grids rely on metal cables to distribute electricity. Home electrical systems, for the most part, are wired with copper wire for its good conducting properties.

The thermal conductivity of metal is useful for containers to heat materials over a flame. Metal is also used for heat sinks to protect sensitive equipment from overheating.

The high reflectivity of some metals is important in the construction of mirrors, including precision astronomical instruments. This last property can also make metallic jewelry aesthetically appealing.

Some metals have specialized uses; Radioactive metals such as Uranium and Plutonium are used in nuclear power plants to produce energy via nuclear fission. Mercury is a liquid at room temperature and is used in switches to complete a circuit when it flows over the switch contacts. Shape memory alloy is used for applications such as pipes, fasteners and vascular stents. However they are very good at conducting electricity and heat.

Trade

The World Bank reports that China was the top importer of ores and metals in 2005 followed by the U.S.A. and Japan.

Astronomy

In the specialised usage of astronomy and astrophysics, the term "metal" is often used to refer to any element other than hydrogen or helium, including substances as chemically non-metallic as neon, fluorine, and oxygen. Nearly all the hydrogen and helium in the Universe was created in Big Bang nucleosynthesis, whereas all the "metals" were produced by nucleosynthesis in stars or supernovae. The Sun and the Milky Way Galaxy are composed of roughly 70% hydrogen, 30% helium, and 2% "metals" by mass.

See also

• ASM International (society)
• Amorphous metal
• Electric field screening
• Metalworking
• Metallic bond
• Metallurgy
• Periodic table (metals and non-metals)
• Properties and uses of metals
• Steel
• Structural steel
• Transition metal

metallic elements

References

External links

• Martindale's "virtual" materials science center -- metals and alloys