Graphite structure?

Question

I know that graphite is molecule that conducts electricity becuase it has free electrons. However, I found that there are only 7 electrons in every graphite's outermost shell . Everything in nature need 8 electrons in their outermost shell to be stable. Isn't it? Who can help me to explain it by the principle of valence shell. Thanks.

Answer 1

In Graphite, each carbon atom is covalently bonded to three other surrounding carbon atoms. Each carbon atom possesses an sp² orbital hybridization. That counts 6 electrons in the outermost shell of every carbon atom. The flat sheets of carbon atoms are bonded into hexagonal structures. There is one more electron in the pi orbital of every carbon atom we have not discussed yet. The electrons of adjacent carbon atoms can also form pi bond. That counts two more electrons in the outermost shell of every carbon atom. Therefore, there are 8 electrons in the outermost shell of every carbon atom, not 7. The pi orbital electrons further delocalize across the hexagonal atomic sheets of carbon, to further reduce energy and thus contribute to graphite's conductivity.