The shape of a graphite crystal is

Analyze the question: It asks about the shape (crystal structure) of graphite, an allotrope of carbon.

Concept: In graphite, each carbon atom is covalently bonded to three other carbon atoms. Each carbon is sp² hybridized, so the bonds lie in a flat plane at 120° to each other. This produces layers made of fused six-membered carbon rings, giving a hexagonal arrangement. The layers are held together by weak van der Waals forces.

Step by step:

• Tetrahedral (A): this is the shape in diamond, where each carbon bonds to four others (sp³). It is not graphite.
• Pyramidal (B): this is a molecular shape, like NH₃, and is not a crystal shape for carbon allotropes.
• Octahedral (C): this is found in some ionic or complex structures, not graphite.
• Hexagonal (D): graphite has planar layers of hexagonal rings, and it crystallizes in the hexagonal system. This matches.

Answer: D. Hexagonal.

Tip: Remember "Diamond = Tetrahedral, Graphite = Hexagonal layers." Graphite's layers slide over each other, which is why it is soft and used as a lubricant and in pencils. Its free (delocalized) electrons also let it conduct electricity.