Bond, bridge nonpolar covalent

In this connection, it is worth mentioning the role of the metallic bonding, which is one of the nonpolar components of the remainii (100 - I)% of the bondii in a semiconductor. X-ray diffraction studies of the distribution of the electron density in metals [15] indicate that free electrons are distributed throughout the whole volume of a crystal. Such a distribution of free electrons fills the dips in the potential more effectively than do the electron "bridges" of the covalent bonds. Therefore, the forbidden band should become narrower, decreasing to zero in the case of a pure metal. 

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