Giant Covalent Structures (OCR GCSE Chemistry A (Gateway))

Giant Covalent Structures

Different types of Covalent Structure

• Covalent bonding can occur between atoms to create small molecules, large molecules or extended giant structures, each with very different physical properties

• Small molecules such as H₂O and N₂ are simple units made from covalently bonded atoms

  • These simple molecules contain fixed numbers of atoms bonded to each other with strong covalent bonds

  • Weak intermolecular forces exist between molecules, so substances are often gases or liquids at room temperature

• Giant covalent structures huge, variable numbers of non-metal atoms bonded to other non-metal atoms via strong covalent bonds

  • There are no weak intermolecular forces present between molecules as there are no molecules, only covalent bonds, so substances are usually solid at room temperature

• Giant covalent structures can also be called giant lattices and have a fixed ratio of atoms in the overall structure

• Three common structures you should know about are diamond, graphite and silicon dioxide

Properties of Giant Covalent Structures

• 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

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