AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Covalent bonding: These bonds between atoms are strong.
The covalent bonds within a molecule are strong because the shared electron pair is attracted to both nuclei.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 2 of 8
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
The covalent bonds within a molecule are strong because the shared electron pair is attracted to both nuclei. Breaking one mole of these bonds needs a large amount of energy, so the bonds do not break during melting or boiling. For example, when water boils, the strong O–H covalent bonds stay intact; the weak forces between separate water molecules are overcome instead. This explains why simple molecular substances have low melting and boiling points even though their covalent bonds are strong. Always distinguish between the strong bonds inside a molecule and the weak intermolecular forces between molecules.
What earns the marks
- Covalent bonds are strong because the shared pair is attracted to both nuclei.
- A large amount of energy is needed to break covalent bonds, so they remain intact during physical changes such as melting and boiling.
- When a simple molecular substance boils, weak forces between molecules are overcome, not the strong covalent bonds within each molecule.
- Strong covalent bonds explain why molecules stay together, while weak intermolecular forces explain low melting and boiling points.
Common mistakes and how to put them right
Saying that covalent bonds break when a simple molecular substance boils.
Put it right by stating that intermolecular forces break instead.
Confusing strong covalent bonds with weak intermolecular forces.
Put it right by naming each type of attraction separately.
Claiming that all attractions in a simple molecular substance are weak.
Put it right by stating that the bonds within each molecule are strong.
Exam tips
- Use the phrase 'strong covalent bonds between atoms' and 'weak forces between molecules' to make the distinction clear.
- When explaining a low boiling point, refer to energy needed to overcome intermolecular forces, not to break covalent bonds.
- Link the strength of a covalent bond to the attraction between the shared pair and both nuclei.
Try the lesson
The start of the Covalent bonding: These bonds between atoms are strong. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement about the covalent bonds between atoms in a molecule is correct?
Listen
The covalent bonds within a molecule are strong because the shared electron pair is attracted to both nuclei. Breaking one mole of these bonds needs a large amount of energy, so the bonds do not break during melting or boiling. For example, when water boils, the strong O–H covalent bonds stay intact; the weak forces between separate water molecules are overcome instead. This explains why simple molecular substances have low melting and boiling points even though their covalent bonds are strong. Always distinguish between the strong bonds inside a molecule and the weak intermolecular forces between molecules. A strong answer earns marks for these points. Covalent bonds are strong because the shared pair is attracted to both nuclei. A large amount of energy is needed to break covalent bonds, so they remain intact during physical changes such as melting and boiling. When a simple molecular substance boils, weak forces between molecules are overcome, not the strong covalent bonds within each molecule. Strong covalent bonds explain why molecules stay together, while weak intermolecular forces explain low melting and boiling points. A common slip: Saying that covalent bonds break when a simple molecular substance boils. Instead, stating that intermolecular forces break instead. Exam tip: Use the phrase 'strong covalent bonds between atoms' and 'weak forces between molecules' to make the distinction clear.
See it
Key words
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Bond strength and energy transfer
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Explaining physical properties of simple molecules
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Attraction between shared electrons and nuclei
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See every definition
- Bond strength and energy transfer
- A large amount of energy is needed to break covalent bonds, so they remain intact during physical changes such as melting and boiling.
- Explaining physical properties of simple molecules
- Strong covalent bonds explain why molecules stay together, while weak intermolecular forces explain low melting and boiling points.
- Attraction between shared electrons and nuclei
- Covalent bonds are strong because the shared pair is attracted to both nuclei.
Label the diagram
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