AQA · A-Level · Chemistry
Course version: 7405 · Version from Sept 2016
Multiple bonds contain multiple pairs of electrons.
Full specification wording
Nature of covalent and dative covalent bonds: Multiple bonds contain multiple pairs of electrons.
A double bond is two shared pairs, four electrons in all, and a triple bond is three shared pairs, six electrons.
Checked against the AQA 7405 specification (opens in a new tab) on .
- Point 2 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A double bond is two shared pairs, four electrons in all, and a triple bond is three shared pairs, six electrons. More shared electrons mean a stronger attraction to both nuclei, so multiple bonds are shorter and stronger than single bonds between the same two atoms: the carbon-carbon bond shortens from ethane to ethene to ethyne while its bond enthalpy rises. When predicting shape, however, a double or triple bond counts as one region of electron density, not two or three, because both pairs lie between the same two nuclei. That is why carbon dioxide, with two double bonds, is linear at 180° rather than bent.
What earns the marks
- A double bond containing two shared pairs of electrons.
- A triple bond containing three shared pairs of electrons.
- Multiple bonds being shorter and stronger than a single bond between the same atoms.
- Treating a multiple bond as a single region of electron density when predicting shape.
Common mistakes and how to put them right
Describing a double bond as two separate single bonds between different atoms.
Drawing three lines for a double bond or two for a triple.
Counting a double bond as two electron pairs when predicting a bond angle, so calling carbon dioxide bent.
Claiming a triple bond is weaker because it is shorter.
Exam tips
- Count electrons, not lines, when a question asks how many electrons are in a bond.
- For shape questions, count regions of electron density: each multiple bond is one region.
- Link bond length and bond enthalpy together when comparing single, double and triple bonds.
Try the lesson
The start of the Nature of covalent and dative covalent bonds: Multiple bonds contain multiple pairs of electrons. lesson, made from checked teaching notes for this specification point.
Have a go first
In an ethene molecule, CH₂=CH₂, how many pairs of electrons are shared between the two carbon atoms?
Listen
A double bond is two shared pairs, four electrons in all, and a triple bond is three shared pairs, six electrons. More shared electrons mean a stronger attraction to both nuclei, so multiple bonds are shorter and stronger than single bonds between the same two atoms: the carbon-carbon bond shortens from ethane to ethene to ethyne while its bond enthalpy rises. When predicting shape, however, a double or triple bond counts as one region of electron density, not two or three, because both pairs lie between the same two nuclei. That is why carbon dioxide, with two double bonds, is linear at 180° rather than bent. A strong answer earns marks for these points. a double bond containing two shared pairs of electrons. a triple bond containing three shared pairs of electrons. multiple bonds being shorter and stronger than a single bond between the same atoms. treating a multiple bond as a single region of electron density when predicting shape. Exam tip: Count electrons, not lines, when a question asks how many electrons are in a bond.
Key words
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double bond
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triple bond
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bond length and strength
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regions of electron density
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See every definition
- double bond
- Contains two shared pairs of electrons, four electrons in all.
- triple bond
- Contains three shared pairs of electrons, six electrons in all.
- bond length and strength
- More shared electrons mean a stronger attraction to both nuclei, so multiple bonds are shorter and stronger than single bonds between the same two atoms.
- regions of electron density
- When predicting shape, a double or triple bond counts as one region, not two or three, because both pairs lie between the same two nuclei.
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