AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
All of the atoms in these structures are linked to other atoms by strong…
Full specification wording
Giant covalent structures: All of the atoms in these structures are linked to other atoms by strong covalent bonds.
A giant covalent structure is a continuous three-dimensional network in which every atom is joined to neighbouring atoms by covalent bonds.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 2 of 5
Study notes
From the checked teaching notes for this specification point.
The idea
A giant covalent structure is a continuous three-dimensional network in which every atom is joined to neighbouring atoms by covalent bonds. Each bond is a shared pair of electrons, so the network has no separate molecules and no overall fixed formula unit. In diamond, each carbon atom forms four single covalent bonds to four other carbon atoms in a tetrahedral arrangement, giving a rigid lattice. In graphite, each carbon atom bonds to three others in hexagonal layers, leaving one delocalised electron per atom. In silicon dioxide, each silicon atom bonds to four oxygen atoms and each oxygen atom bonds to two silicon atoms, so the ratio is 1:2 but the network is continuous. Because bonding extends throughout the structure, melting involves breaking many strong covalent bonds rather than separating small molecules.
What earns the marks
- A giant covalent structure is a continuous network of atoms joined by covalent bonds, not a collection of separate small molecules.
- Each covalent bond is a shared pair of electrons between two non-metal atoms, for example C–C or Si–O bonds.
- In diamond, each carbon atom forms four single covalent bonds arranged tetrahedrally, so every atom is linked into the network.
- In graphite, each carbon atom forms three covalent bonds within a hexagonal layer, with one delocalised electron per carbon atom.
- In silicon dioxide, each silicon atom is bonded to four oxygen atoms and each oxygen atom is bonded to two silicon atoms, giving a 1:2 ratio in a continuous network.
- The strength and number of covalent bonds throughout the structure explain the very high melting points of these substances.
Common mistakes and how to put them right
Describing giant covalent structures as containing small molecules joined together.
Put it right by stating that the whole structure is one continuous covalent network with no separate molecules.
Drawing or describing graphite as if each carbon atom forms four bonds to other carbon atoms.
Put it right by showing three bonds per carbon atom within a layer and one delocalised electron per atom.
Treating silicon dioxide as simple molecules of SiO₂.
Put it right by describing a continuous network in which each silicon atom bonds to four oxygen atoms and each oxygen atom bonds to two silicon atoms.
Exam tips
- When a diagram is given, count the bonds around a labelled atom and state the number explicitly, for example four bonds around each carbon atom in diamond.
- Use the phrase continuous giant covalent network rather than molecule when describing diamond, graphite or silicon dioxide.
- Link the bonding directly to a property, such as explaining a high melting point by the many strong covalent bonds that must be broken.
Try the lesson
The start of the Giant covalent structures: All of the atoms in these structures are linked to other atoms by strong covalent bonds. lesson, made from checked teaching notes for this specification point.
Have a go first
In a giant covalent structure, how is each atom joined to the other atoms around it?
Listen
A giant covalent structure is a continuous three-dimensional network in which every atom is joined to neighbouring atoms by covalent bonds. Each bond is a shared pair of electrons, so the network has no separate molecules and no overall fixed formula unit. In diamond, each carbon atom forms four single covalent bonds to four other carbon atoms in a tetrahedral arrangement, giving a rigid lattice. In graphite, each carbon atom bonds to three others in hexagonal layers, leaving one delocalised electron per atom. In silicon dioxide, each silicon atom bonds to four oxygen atoms and each oxygen atom bonds to two silicon atoms, so the ratio is 1:2 but the network is continuous. Because bonding extends throughout the structure, melting involves breaking many strong covalent bonds rather than separating small molecules. A strong answer earns marks for these points. A giant covalent structure is a continuous network of atoms joined by covalent bonds, not a collection of separate small molecules. Each covalent bond is a shared pair of electrons between two non-metal atoms, for example C–C or Si–O bonds. In diamond, each carbon atom forms four single covalent bonds arranged tetrahedrally, so every atom is linked into the network. In graphite, each carbon atom forms three covalent bonds within a hexagonal layer, with one delocalised electron per carbon atom. A common slip: Describing giant covalent structures as containing small molecules joined together. Instead, stating that the whole structure is one continuous covalent network with no separate molecules. Exam tip: When a diagram is given, count the bonds around a labelled atom and state the number explicitly, for example four bonds around each carbon atom in diamond.
See it
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Giant covalent structures: All of the atoms in these structures are linked to other atoms by strong covalent bonds.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge