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CONDUCTORS, SEMICONDUCTORS, and INSULATORS are categorized as such by using
the energy band concept. It is the width of the forbidden band that determines whether a material is an
insulator, a semiconductor, or a conductor. A CONDUCTOR has a very narrow forbidden band or none at
all. A SEMICONDUCTOR has a medium width forbidden band. An INSULATOR has a wide forbidden
band.
COVALENT BONDING is the sharing of valence electrons between two or more atoms. It is this
bonding that holds the atoms together in an orderly structure called a CRYSTAL.
