Which of the following non-metals is a good conductor of electricity in the solid state due to the presence of delocalized electrons within its crystal lattice?

Graphite is the only non-metal in this list that is a good conductor of electricity in the solid state because of its unique structure containing delocalized electrons. In graphite, each carbon atom is bonded to only three other carbon atoms in a hexagonal layer, leaving one free valence electron per atom. These free electrons are delocalized and can move freely between the layers of the crystal lattice, allowing the flow of electric current. Although diamond is also made of carbon, all four of its valence electrons are locked in strong covalent bonds, making it an insulator.