Lecture on Allotropes of Carbon: Diamond and Graphite

Introduction

• Allotropes: Different structural forms of the same element in the same physical state.
• Examples: Carbon allotropes include diamond, graphite, graphene, and fullerenes.
• Focus: Today's lecture covers diamond and graphite; graphene and fullerenes will be in the next lecture.

Diamond

• Structure: Diamond is a giant covalent structure with a regular 3D pattern.
  • Each carbon atom is covalently bonded to four other carbon atoms (maximum for carbon).
• Properties:
  • Strength: Strong covalent bonds require high energy to break, making diamond very strong.
  • Melting Point: High melting point due to strong covalent bonds.
  • Electrical Conductivity: Does not conduct electricity as there are no free electrons or ions.

Graphite

• Structure: Graphite is a giant covalent structure with hexagonal arrangements of atoms.
  • Each carbon atom is bonded to three other carbon atoms.
  • Forms large flat sheets layered on top of each other.
  • Layers are held together weakly as there are no covalent bonds between them.
• Properties:
  • Softness: Layers can slide over one another, making graphite relatively soft compared to diamond.
  • Melting Point: Still high due to strong covalent bonds within the layers.
  • Electrical Conductivity: Conducts electricity and heat due to delocalized electrons (one spare electron per carbon atom not used in bonding).

Graphene

• Definition: A single layer of graphite known as graphene.
• Applications: Isolated graphene layers can be used to create other structures like spheres and tubes.

Conclusion

• Summary: Key differences in structure and properties of diamond and graphite.
• Next Steps: Further examination of graphene and fullerenes in the next video.

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