Covalent Bonding

• Covalent bonds involve 2 non-metals sharing electrons by fitting together in order to ensure that all atoms have full outer shells
• Simple molecular substances are small molecules in which the atom in the molecule are joined by strong covalent bonds but between the individual molecules there are weak intermolecular forces which are easily broken
• Covalent bonds can also be used to make larger structures like polymers and giant covalent structures
• Polymers are large molecules made up from many repeating units called monomers, they are held together by strong covalent bonds
• Giant covalent structures are very large structures with lots of atoms bonded together by strong covalent bonds and are generally arranged into regular repeating lattices
• The properties of simple molecular substances depend on their structure - size, shape, arrangement of atoms within the molecule and how these molecules interact with one another
• Covalent bonds are really strong which means a lot of energy is going to be needed to break apart any of the atoms that aree covalently bonded together
• • Properties of Simple Molecular Substances:
  • Low melting/boiling point: In order to melt/boil simple molecular substances, there will be a need to break the weak intermolecular forces that exist between molecules which is why there is a need for only low temperatures
• Properties of Simple Molecular Substances:

  • Cant conduct Electricity : There are no free electrons and the molecules don't have an electric charge
• Properties of Giant Covalent Structures:

  • High melting/boiling points as there would be a need to break all the strong covalent bonds in order to break them apart
  • Don't conduct electricity as they don't contain any charged particles even when they are molten except graphite
• Allotropes

  Different structural forms of the same element in the same physical state
• Allotropes of carbon

  • Diamond
  • Graphite
  • These 2 are giant covalent structures which means they are made from a regular lattice of covalently bonded atoms which makes them very strong
  • Graphene
  • Fullerenes
• Diamond


  • Giant covalent structure
  • Each carbon atom is covalently bonded to four other carbon atoms
  • Very strong
  • High melting point
  • Does not conduct electricity as it has no free electrons to move around
• Graphite


  • Giant covalent structure
  • Each carbon atom is covalently bonded to three other carbon atoms
  • Arranged in hexagons forming flat sheets which are arranged on top of one another to form layers
  • Layers are weakly held together as there are no covalent bonds between them which means that they are free to slide over one another
  • Relatively soft compared to diamond
  • High melting point
  • Conducts electricity and heat as individual layers are strongly held togther with covalent bonds
• Delocalized electrons


  Electrons that are free to move around in graphite which help to conduct electricity and heat
• Graphene


  A single layer of graphite
• Scientists can isolate individual layers of graphite (graphene) and use them to make other structures such as spheres and tubes, which are called fullerenes
• Allotropes

  Different structural forms of the same element in the same physical state
• Graphene


  • Made up of layers
  • Structure of multiple repeating hexagons
  • Each carbon bonded to 3 other carbons
  • Donates one electron to a delocalized pool
  • Can conduct electricity so used during making electronics
• Fullerenes

  Tiny tubes and spheres made of carbon
• Fullerenes

  • Large surface area to volume ratio
  • Can be used to deliver drugs
  • Can be used as industrial catalysts
  • Can strengthen other materials due to high length to diameter ratio