Giant Covalent Structures (AQA GCSE Chemistry: Combined Science)

• Covalent bonding can be responsible for substances that have many different structures and therefore different physical properties
• We have already seen how small molecules such as H₂O and N₂ are simple units made from covalently bonded atoms
• These simple molecules contain fixed numbers of atoms
• Giant covalent structures on the other hand have a huge number of non-metal atoms bonded to other non-metal atoms via strong covalent bonds
• These structures can also be called giant lattices and have a fixed ratio of atoms in the overall structure
• Three common macromolecules you should know about are diamond, graphite and silicon dioxide

• They have high melting and boiling points as they have many strong covalent bonds
• Large amounts of heat energy are needed to overcome these forces and break down bonds
• Most cannot conduct electricity as they do not have free electrons nor charged particles but there are some exceptions such as graphite and graphene
• Diamond, graphite, buckminsterfuller and graphene are all made from carbon

Some giant covalent structures and their properties. Although Buckminsterfullerene is not a giant structure it provides a good illustration of how different forms of the same element, carbon in this case, can form simple molecules and giant lattices