Electric conductors nonmetal solid state

Properties of nonmetals are more varied than those of metals. A number of nonmetals are gases in the elemental state hydrogen, oxygen, nitrogen, fluorine, chlorine, and the noble gases. Only one, bromine, is a liquid. All the remaining nonmetals are solids at room temperature. Unlike metals, nonmetallic elements are poor conductors of heat and electricity they exhibit both positive and negative oxidation numbers. 

Crystalline nonmetals, such as diamond and phosphorus, are insulators—they do not conduct electricity. The reason for this is that their highest energy electrons occupy filled hands of molecular orhitals that are separated from the lowest empty band (conduction band) by an energy difference called the band gap (Eg). In an insulator, this band gap is an energy difference that is too large for electrons to jump to get to the conduction band (Figure 13-35). Many ionic solids are also insulators, but are good conductors in their molten (liquid) state. 

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