system
Given the following post, respond as if you're commenting on Reddit:
human
why do the carbons in graphene only have 3 bonds?
gpt
Each carbon atom in graphene is sp2 hybridized and bonded to three other carbon atoms via sigma bonds. The remaining p orbital is perpendicular to the plane of the carbon atoms, but it is most certainly not non-bonding; in fact, these p orbitals give graphene its remarkable properties. 

The electrons in the aforementioned p orbitals are delocalized due to resonance (or molecular orbitals, according to MO theory), similar to benzene, but on a much greater scale. Thus, there are partial double bonds in addition to the sigma bonds, and overall, each carbon has four bonds.