AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Diamond and graphite (forms of carbon) and silicon dioxide (silica) are…
Full specification wording
Giant covalent structures: Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures.
Diamond, graphite and silicon dioxide are the three named examples of giant covalent structures.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 4 of 5
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Diamond, graphite and silicon dioxide are the three named examples of giant covalent structures. Diamond and graphite are both made only of carbon atoms but have different arrangements, so they are allotropes with different properties. In diamond, each carbon atom forms four single covalent bonds in a rigid tetrahedral network, making diamond very hard and giving it a very high melting point. In graphite, each carbon atom forms three covalent bonds in hexagonal layers, with delocalised electrons between layers, so graphite conducts electricity and layers can slide. Silicon dioxide contains silicon and oxygen in a continuous network in which each silicon atom bonds to four oxygen atoms and each oxygen atom bonds to two silicon atoms. These examples show how the same type of bonding can produce different properties when the arrangement differs.
What earns the marks
- Diamond and graphite are both forms of carbon and are examples of giant covalent structures.
- Diamond has a rigid three-dimensional network in which each carbon atom forms four single covalent bonds.
- Graphite has hexagonal layers in which each carbon atom forms three covalent bonds, with delocalised electrons between the layers.
- Silicon dioxide, also called silica, is a giant covalent structure of silicon and oxygen atoms in a continuous network.
- Diamond and graphite are allotropes of carbon, meaning they contain only carbon atoms but have different structural arrangements.
- The different arrangements in diamond and graphite lead to different properties, such as hardness and electrical conductivity.
Common mistakes and how to put them right
Treating diamond and graphite as different elements.
Put it right by stating that both are forms of carbon and are allotropes of the same element.
Describing graphite as a simple molecular substance because it has layers.
Put it right by stating that each layer is a giant covalent network and the whole structure is giant covalent.
Writing silicon dioxide as separate SiO₂ molecules.
Put it right by describing a continuous network of silicon and oxygen atoms with each silicon atom bonded to four oxygen atoms.
Exam tips
- Name all three examples when asked for giant covalent structures: diamond, graphite and silicon dioxide.
- When comparing diamond and graphite, refer to the number of covalent bonds per carbon atom and the resulting arrangement.
- Use the term allotrope correctly to describe diamond and graphite as different structural forms of carbon.
Try the lesson
The start of the Giant covalent structures: Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures. lesson, made from checked teaching notes for this specification point.
Have a go first
Which set of substances are all examples of giant covalent structures?
Listen
Diamond, graphite and silicon dioxide are the three named examples of giant covalent structures. Diamond and graphite are both made only of carbon atoms but have different arrangements, so they are allotropes with different properties. In diamond, each carbon atom forms four single covalent bonds in a rigid tetrahedral network, making diamond very hard and giving it a very high melting point. In graphite, each carbon atom forms three covalent bonds in hexagonal layers, with delocalised electrons between layers, so graphite conducts electricity and layers can slide. Silicon dioxide contains silicon and oxygen in a continuous network in which each silicon atom bonds to four oxygen atoms and each oxygen atom bonds to two silicon atoms. These examples show how the same type of bonding can produce different properties when the arrangement differs. A strong answer earns marks for these points. Diamond and graphite are both forms of carbon and are examples of giant covalent structures. Diamond has a rigid three-dimensional network in which each carbon atom forms four single covalent bonds. Graphite has hexagonal layers in which each carbon atom forms three covalent bonds, with delocalised electrons between the layers. Silicon dioxide, also called silica, is a giant covalent structure of silicon and oxygen atoms in a continuous network. A common slip: Treating diamond and graphite as different elements. Instead, stating that both are forms of carbon and are allotropes of the same element. Exam tip: Name all three examples when asked for giant covalent structures: diamond, graphite and silicon dioxide.
See it
Key words
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Allotropes of carbon
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Giant covalent structures
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Structure–property relationships
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See every definition
- Allotropes of carbon
- Forms such as diamond and graphite that contain only carbon atoms but have different structural arrangements.
- Giant covalent structures
- Structures such as diamond, graphite and silicon dioxide, in which atoms are held in a continuous network by covalent bonds.
- Structure–property relationships
- The way the arrangement of atoms in a structure leads to different properties, such as hardness and electrical conductivity.
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