AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
These substances do not conduct electricity because the molecules do not…
Full specification wording
Properties of small molecules: These substances do not conduct electricity because the molecules do not have an overall electric charge.
Simple molecular substances do not conduct electricity in any state because their molecules are neutral overall.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 5 of 6
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Simple molecular substances do not conduct electricity in any state because their molecules are neutral overall. A molecule such as methane (CH₄) contains covalent bonds, but the shared electrons are held between the atoms and are not free to move through the substance. There are no charged particles, such as ions or delocalised electrons, that can carry charge. Even though individual atoms in a bond may carry small partial charges, the molecule as a whole has no overall electric charge. This is why substances like water, carbon dioxide and iodine do not conduct electricity, unlike ionic compounds when molten or dissolved, or metals and graphite which contain delocalised electrons.
What earns the marks
- Simple molecular substances contain neutral molecules with no overall charge.
- There are no free ions or delocalised electrons to carry charge.
- Covalent bonds hold atoms together within molecules but do not provide mobile charge carriers.
- Conduction requires charged particles that are free to move.
Common mistakes and how to put them right
Thinking that covalent bonds allow conduction because electrons are shared.
Put it right: Shared electrons are localised and not free to move through the substance.
Confusing simple molecular substances with ionic compounds.
Put it right: Ionic compounds conduct when molten or dissolved because their ions are free to move.
Believing that all non-metals cannot conduct.
Put it right: Graphite, a non-metal, conducts because it has delocalised electrons.
Exam tips
- Refer explicitly to the absence of free ions or delocalised electrons as the reason for no conduction.
- Avoid saying molecules have no charge at all; state that they have no overall electric charge.
- Contrast with a conducting substance, such as a molten ionic compound, to show understanding.
Try the lesson
The start of the Properties of small molecules: These substances do not conduct electricity because the molecules do not have an overall electric charge. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement explains why simple molecular substances do not conduct electricity?
Listen
Simple molecular substances do not conduct electricity in any state because their molecules are neutral overall. A molecule such as methane (CH₄) contains covalent bonds, but the shared electrons are held between the atoms and are not free to move through the substance. There are no charged particles, such as ions or delocalised electrons, that can carry charge. Even though individual atoms in a bond may carry small partial charges, the molecule as a whole has no overall electric charge. This is why substances like water, carbon dioxide and iodine do not conduct electricity, unlike ionic compounds when molten or dissolved, or metals and graphite which contain delocalised electrons. A strong answer earns marks for these points. Simple molecular substances contain neutral molecules with no overall charge. There are no free ions or delocalised electrons to carry charge. Covalent bonds hold atoms together within molecules but do not provide mobile charge carriers. Conduction requires charged particles that are free to move. A common slip: Thinking that covalent bonds allow conduction because electrons are shared. Instead, shared electrons are localised and not free to move through the substance. Exam tip: Refer explicitly to the absence of free ions or delocalised electrons as the reason for no conduction.
See it
Key words
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Neutral molecules
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Charge carriers
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Covalent bonding
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See every definition
- Neutral molecules
- Molecules that have no overall electric charge, even though individual atoms in a bond may carry small partial charges.
- Charge carriers
- Charged particles, such as ions or delocalised electrons, that are free to move and are required for conduction.
- Covalent bonding
- Bonds that hold atoms together within molecules, with shared electrons held between the atoms and not free to move through the substance.
Label the diagram
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1Box 1
2Box 2
3Box 3
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