AQA GCSE Chemistry

Revision Notes

2.2.7 Giant Covalent Structures

Structure: Giant Covalent Substances

  • 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

Exam Tip

Giant covalent structures can also be called macromolecules.

Properties: Giant Covalent Substances

  • 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

Comparison of the properties giant covalent compounds table, downloadable IB Chemistry revision notes

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

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.

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