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Why Graphite can conduct electricity?
Why it is GOOD electrical conductor?
Graphite's crystal structure is made up of 2-D sheets of interlocking 6-membered benzene-like rings of carbons. The delocalized pi-bonding orbitals (ring structure is sp2) interact weakly in between layers to hold adjacent layers together. These half-full pi-orbitals are the obvious choice for the conduction band, and a quick sketch of the band diagram for graphite confirms this, having (in lowest to highest energy) a full sp2 bonding orbital followed by a small band gap, and then the half-full nonbonding pi system, followed by a band gap, and then the empty antibonding sp2 hybrid orbitals. This is why graphite is a conductor, and the fact that the pi-system is half full makes it a good conductor, although only along the planes of the 2-D sheets. Hope this answers your question.
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