| Metal,
derived from the Greek word 'metallon' meaning "mine, quary,
ore, metal" is an element that readily forms positive ions
and has metallic bonds. Currently, there are 86 known metals,
24 of which were discovered before the 19th century. Metals account
for about two-thirds of all elements and about 24% of the mass
of the planet. Because of their properties, such as strength,
ductility, high melting point, thermal and electrical conductivity,
and toughness, metals have become the most widely used material
in the world.
A modern
definition of metals is that they have overlapping conduction
bands and valence bands in their electronic structure. This definition
opens up the category for metallic polymers and other organic
materials, which have been made by researchers and employed in
high tech devices. These synthetic materials often have the characteristic
silvery-grey reflectiveness of elemental metals.
Some
examples are golf, jewelry, copper wire, steel and steel alloys
used in construction or automotive structure, and aluminium products.
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Metals