Which form of carbon involves each carbon atom being bonded to three others in flat layers?

• A. Diamond
• B. Graphite
• C. Fullerene
• D. Nanotube

Answer: (B)

Carbon can form different structures, and in graphite each carbon atom forms three bonds in a single plane. These bonds create flat sheets of connected carbon atoms arranged in a hexagonal lattice, known as graphene layers. The remaining valence electron is delocalized across the layer, giving electrical conductivity along the sheets. The layers are held together by weaker van der Waals forces, so they can slide past each other, which also explains graphite’s lubricating properties. Other forms differ in how the carbon atoms connect: diamond makes a rigid three-dimensional network where each carbon bonds to four neighbors; fullerenes are spherical cages; nanotubes are rolled-up sheets forming tubes. The description of three in-plane bonds forming flat layers points to graphite.