metal
- (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.
- (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.
Related category
INORGANIC
CHEMISTRY
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