1.4.8

Giant Covalent Structures

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Diamond

Diamond is an allotrope (form) of carbon. Diamond has the following properties:

Covalent bonds

Covalent bonds

  • Each carbon atom in diamond is bonded to four other carbon atoms by strong covalent bonds.
    • This creates a giant covalent structure.
Hard

Hard

  • There are lots of strong covalent bonds in diamond. This makes it very hard.
    • Because diamond is hard, it is used as a cutting tool to cut other materials.
Does NOT conduct electricity

Does NOT conduct electricity

  • Diamond does NOT conduct electricity because there are no delocalised electrons in the diamond structure.
High melting point

High melting point

  • A lot of energy is needed to break strong covalent bonds.
  • Diamond has lots of strong covalent bonds. This means that it has a high melting point.
Thermal conductivity

Thermal conductivity

  • Diamond has a very rigid structure.
    • This means that vibrations can easily carry heat throughout the structure.
    • Diamond is an excellent thermal conductor.

Graphite

Graphite is an allotrope (form) of carbon. Graphite has the following properties:

Covalent bonds

Covalent bonds

  • Each carbon atom in graphite is bonded to 3 other carbon atoms by strong covalent bonds.
    • This creates a giant covalent structure.
Strong covalent bonds

Strong covalent bonds

  • Due to the strong covalent bonds within the sheets, graphite:
    • Has a high melting point.
    • Is insoluble in solvents.
Soft

Soft

  • The carbon atoms form layers of hexagonal (6-sided) rings, with each layer held together by weak intermolecular forces.
  • The layers can slide over one another easily, so graphite is very soft.
    • This makes it useful as a lubricant and as pencil ‘lead’.
Conducts electricity

Conducts electricity

  • Each carbon atom forms 3 covalent bonds.
  • 1 electron from every carbon atom in graphite is delocalised.
  • This electron can move freely, so graphite can conduct electricity.

Silicon

Silicon is a nonmetal in group 4 - the same group as carbon. Silicon has the following properties:

Structure

Structure

  • Pure silicon is structured in the form of a giant covalent structure.
  • Silicon atoms are held together in a giant covalent lattice, with each atom bonded to four other silicon atoms.
    • This is the same structure as that of carbon so silicon also has very high melting and boiling points.
Conductivity

Conductivity

  • Silicon does conduct electricity as it is a semiconductor.
    • Silicon conducts electricity in a different way to metals.
Jump to other topics
1

Physical Chemistry

1.1

Atoms, Molecules & Stoichiometry

1.2

Atomic Structure

1.3

Chemical Bonding

1.4

States of Matter

1.5

Chemical Energetics

1.6

Electrochemistry

1.7

Equilibria

1.8

Partition Coefficient

1.9

Reaction Kinetics

2

Inorganic Chemistry

3

Organic Chemistry & Analysis

3.1

Introduction to Organic Chemistry

3.2

Hydrocarbons

3.3

Halogen Derivatives

3.4

Hydroxy Compounds

3.5

Carbonyl Compounds

3.6

Carboxylic Acids & Derivatives

3.7

Nitrogen Compounds

3.8

Polymerisation

3.9

Analytical Techniques

3.10

Organic Synthesis

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