Diamond, graphite and silicon dioxide, then graphene, fullerenes and nanotubes, and how structure decides hardness, melting point and conduction.
What you will learn
- Explain the very high melting points of giant covalent structures
- Compare diamond and graphite and link structure to properties and uses
- Identify a structure type from property data
Every atom bonded to its neighbours
In a giant covalent structure there are no separate molecules: every atom is joined to others by strong covalent bonds, on and on through the whole solid.
Melting means breaking huge numbers of these bonds, so the melting points are very high (diamond about 3550 °C, silicon dioxide about 1710 °C).
- Diamond: each carbon bonded to four others in a rigid 3D network. Very hard, very high melting point, does not conduct (no free electrons).
- Silicon dioxide (silica, found as sand and quartz): each silicon bonded to four oxygens, each oxygen to two silicons.
- Graphite: each carbon bonded to three others in flat layers of hexagonal rings.
The rest of this lesson and its 9 practice questions are locked.
In this lesson
- Every atom bonded to its neighbours
- Graphite: layers and loose electrons
- Graphene, fullerenes and nanotubes
- Which structure is it?
- Try it: Sort the four solids
9 practice questions, marked as you go; about 24 minutes in all.
Key terms
Giant covalent structure
In this unit: Bonding, structure and the properties of matter
Ionic, covalent and metallic bonding, the structures they make, and how structure explains melting points, conduction and hardness, with nanoparticles for separate Chemistry.
- Ionic bonding and ionic formulae
- Ionic lattices and covalent bonds
- Simple molecules and polymers
- Giant covalent structures and forms of carbon
- Metallic bonding and alloys
- Nanoparticles