Structure and Properties of Two Allotropes of Carbon: Diamond and Graphite

What are Allotropes?

• Allotropes: Different structural forms of the same element in the same physical state.
• Examples in carbon: Diamond, graphite, fullerenes, and graphene.

Giant Covalent Structures

• Diamond and graphite are both giant covalent structures.
• Composed of a regular lattice of covalently bonded atoms.
• Both are very strong due to strong covalent bonds.

Diamond

• Each carbon atom is covalently bonded to four other carbon atoms.
• Forms a regular 3D pattern.
• *Properties:
  • Very strong and high melting point.
  • Does not conduct electricity (no free electrons or ions).*

Graphite

• Each carbon atom is bonded to three other carbon atoms.
• Atoms arranged in hexagons forming large flat sheets, stacked in layers.
• *Properties:
  • Layers held weakly together (can slide over each other).
  • Relatively soft compared to diamond.
  • High melting point.
  • Conducts electricity and heat (one free electron per carbon atom; delocalized electrons).*

Graphene and Fullerenes

• A single layer of graphite is called graphene.
• Can be isolated to make structures such as spheres and tubes.
• Further details to be covered in the next video.

Note: Fullerenes and other smaller allotropes will be explored in the next video.

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