2.6 Giant Covalent Structures

2026 Syllabus Objectives

Core:

  1. Describe the giant covalent structures of graphite and diamond
  2. Relate the structures and bonding of graphite and diamond to their uses, limited to:
    • (a) graphite as a lubricant and as an electrode
    • (b) diamond in cutting tools

Supplement: 3. Describe the giant covalent structure of silicon(IV) oxide, SiO2\mathrm{SiO_2} 4. Describe the similarity in properties between diamond and silicon(IV) oxide, related to their structures

What are Giant Covalent Structures? 🔑

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Giant covalent structures are substances where large numbers of atoms are held together by covalent bonds forming a strong lattice structure. Unlike simple molecular structures, these structures repeat in all directions with the same forces holding the entire structure together.

Key characteristics of giant covalent structures:

  • The structure repeats itself in all directions
  • Strong covalent bonds extend throughout the entire crystal
  • The forces involved are the same in all directions
  • Held together by strong covalent bonds forming a lattice

Examples of giant covalent structures:

  • Carbon in the form of diamond and graphite
  • Silicon(IV) oxide (silica, SiO2\mathrm{SiO_2}) found in sand and quartz

Giant molecular crystals are held together by strong covalent bonds extending throughout the structure.

Diamond Structure and Properties 💎

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Structure of Diamond

Diamond has a tetrahedral structure where each carbon atom is bonded to four other carbon atoms. The atoms are arranged tetrahedrally with strong covalent bonds extending in all directions through the whole crystal.

Key structural features:

  • Each carbon atom forms 4 covalent bonds with 4 other carbon atoms
  • Atoms arranged in a tetrahedral pattern
  • All atoms bonded to each other throughout the structure
  • Rigid three-dimensional network
  • No free electrons - all outer electrons used for covalent bonding

Properties of Diamond

1. Very High Melting Point

  • Strong covalent bonds extend throughout the whole structure
  • These bonds require enormous amounts of energy to break
  • Bonding extends throughout the entire crystal lattice

2. Extremely Hard

  • Hardest natural substance
  • Strong covalent bonds in all directions
  • Each carbon atom bonded to four others
  • However, the structure is brittle due to rigid bonds

3. Does Not Conduct Electricity

  • All outer electrons are used to form covalent bonds
  • No free electrons available to move and carry charge
  • Diamond is a typical non-metallic element

4. Appearance

  • Colourless, transparent crystals
  • Sparkle in light

Uses of Diamond ⚡

Diamond's unique properties make it valuable for specific applications:

PropertyUse
Extremely hardCutting tools - drill bits, diamond saws, glass-cutters
Hardest natural substanceIndustrial cutting and grinding applications
Transparent and sparklesJewellery and ornamental objects

The extreme hardness of diamond results from strong covalent bonds extending in all directions throughout the structure.

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