INORGANIC CHEMISTRY

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metal

1. (CHEMISTRY) A material in which the highest occupied energy band (conduction band) is only partially filled with electrons. In terms of physical properties, metals:
   
   • Are good conductors of heat and electricity. The electrical conductivity of metals generally decreases with temperature
   • Are malleable and ductile in their solid state
   • Show metallic luster
   • Are opaque
   • Have high density
   • Are solids (except mercury)
   • Have crystal structure in which each atom is surrounded by eight to twelve near neighbors
     
   In terms of their chemical properties, metals:
   
   • Have one to four valence electrons
   • Have low ionization potentials; they readily lose electrons
   • Are good reducing agents
   • Have hydroxides that are bases or amphoteric
   • Are electropositive
     
   Metallic characteristics of the elements decrease and non-metallic characteristics increase with the increase of valence electrons. Also metallic characteristics increase with the number of electron shells. Therefore, there is no sharp dividing line between the metals and the non-metals. Of the 113 elements now known, only 17 show primarily non-metallic characteristics (see nonmetal), 7 others are metalloids, and 89 may be classed as metals.
   
   Most metals are found as ores; only a few, such as gold and silver, occur in a native state. Alloys are easily formed because of the nonspecific nondirectional nature of the metallic bond.



2. (ASTRONOMY & ASTROPHYSICS) Any element heavier than hydrogen and helium. An object's metallicity is its abundance of such elements, or, often, more specifically, the abundance of iron, which is easy to measure. The terms metal-poor and metal-rich are used to indicate low metallicity and high metallicity, respectively.

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