Covalent bonding

• A covalent bond is formed between atoms by sharing a pair of electrons
• There is strong electrostatic attraction between the negatively charged electrons and the positively charged nuclei
• Substances with simple molecular bonds have low melting and boiling points because there are weak intermolecular forces between particles
• The melting and boiling points of substances with simple molecular structures increase with increasing molecular mass due to the greater number of bonds and higher amount I’ve energy needed to break them between the atoms
• Giant covalent structures are solids with high melting and boiling points due to the strong covalent bonds between particles
• Covalent compounds do not usually conduct electricity
• Diamond:

  • made of a network of carbon atoms each with four bonds
  • has a very high melting point due to strong covalent bonds
  • cannot conduct electricity
• Graphite:

  • each carbon atom only has three bonds between particles
  • structured in layers
  • layers are held together by weak IMF
  • each carbon atom has a delocalised electron
  • the delocalised electron can carry charge
• C60 fullerene:

  • Hollow sphere made of 60 carbon atoms
  • molecules only held together by IMFs, so it is very soft
  • each atom has one delocalised electron, but the electrons can’t move between molecules, so it is a poor conductor of electricity
  • used for transporting drugs into the body, catalysts and lubricants