C3.7 - Giant covalent structures

• Some covalently bonded substances have giant structures
• Giant structures have very high melting and boiling points
• Giant covalent structures substances properties:

  • they have a very high melting and boiling point
  • they are insoluble in water
  • they are hard and do not conduct electricity (NOT including GRAPHITE)
• Graphite:

  • contains layers of covalently bonded carbon atoms
  • However there are no covalent bond between the layers only weak intermolecular forces
  • This means the layers can slide over each other quickly, making graphite soft and slippery
  • can conduct electricity and thermal energy because of the delocalised electrons that can move along its layers
  • high melting point and boiling point
• Delocalised electrons are electrons that are free to move within the solid.
• Diamond:

  • cannot conduct electricity because they have no free electrons, as all their outer shell electrons are involved in covalent bonding
  • hard because it has very strong bonds that have to be broken
  • high melting point and boiling point because they had very strong covalent bonds