AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Ions are discharged at the electrodes producing elements.
Full specification wording
The process of electrolysis: Ions are discharged at the electrodes producing elements.
During electrolysis, ions in an electrolyte move to the electrode of opposite charge.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 5 of 7
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
During electrolysis, ions in an electrolyte move to the electrode of opposite charge. Positive ions (cations) are attracted to the negative cathode, where they gain electrons and are discharged as neutral atoms. Negative ions (anions) are attracted to the positive anode, where they lose electrons and are discharged as neutral atoms. For example, in molten lead bromide, Pb²⁺ ions gain electrons at the cathode to form lead metal, while Br⁻ ions lose electrons at the anode to form bromine molecules. The discharge of ions produces elements because the neutral atoms formed are the elements themselves. This process requires a direct current supply. Inert electrodes are often used so they do not react, but reactive electrodes are sometimes used, such as carbon anodes in aluminium extraction.
What earns the marks
- Cations (positive ions) move to the cathode (negative electrode) and gain electrons to form neutral atoms.
- Anions (negative ions) move to the anode (positive electrode) and lose electrons to form neutral atoms.
- Discharge produces elements because the neutral atoms formed are the elements themselves.
- The electrolyte must contain mobile ions, either molten or in aqueous solution.
- Electrodes can be inert (like platinum) to prevent reaction, or reactive (like carbon in aluminium extraction) depending on the process.
Common mistakes and how to put them right
Confusing the polarity of electrodes.
Put it right: 'cations go to cathode' and 'anions go to anode'.
Thinking that ions gain or lose protons rather than electrons.
Put it right: Discharge involves electron transfer, not proton transfer.
Assuming that solid ionic compounds conduct electricity.
Put it right: The ions must be mobile, so the compound must be molten or dissolved in water.
Exam tips
- When describing discharge, always state the electrode, the ion, and whether electrons are gained or lost.
- Use the terms cation and anion correctly to show understanding of charge.
- Link the discharge to the formation of a neutral element, naming the product.
Try the lesson
The start of the The process of electrolysis: Ions are discharged at the electrodes producing elements. lesson, made from checked teaching notes for this specification point.
Have a go first
During the electrolysis of molten potassium chloride, potassium ions move to the cathode. What is produced at the cathode?
Listen
During electrolysis, ions in an electrolyte move to the electrode of opposite charge. Positive ions (cations) are attracted to the negative cathode, where they gain electrons and are discharged as neutral atoms. Negative ions (anions) are attracted to the positive anode, where they lose electrons and are discharged as neutral atoms. For example, in molten lead bromide, Pb²⁺ ions gain electrons at the cathode to form lead metal, while Br⁻ ions lose electrons at the anode to form bromine molecules. The discharge of ions produces elements because the neutral atoms formed are the elements themselves. This process requires a direct current supply. Inert electrodes are often used so they do not react, but reactive electrodes are sometimes used, such as carbon anodes in aluminium extraction. A strong answer earns marks for these points. Cations (positive ions) move to the cathode (negative electrode) and gain electrons to form neutral atoms. Anions (negative ions) move to the anode (positive electrode) and lose electrons to form neutral atoms. Discharge produces elements because the neutral atoms formed are the elements themselves. The electrolyte must contain mobile ions, either molten or in aqueous solution. A common slip: Confusing the polarity of electrodes: the cathode is negative and attracts positive ions; the anode is positive and attracts negative ions. Instead, 'cations go to cathode' and 'anions go to anode'. Exam tip: When describing discharge, always state the electrode, the ion, and whether electrons are gained or lost.
See it
Key words
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Electrolysis
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Ionic conduction
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Electrode processes
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See every definition
- Electrolysis
- A process in which ions in an electrolyte move to the electrode of opposite charge and are discharged, requiring a direct current supply.
- Ionic conduction
- The movement of mobile ions, either molten or in aqueous solution, towards the electrode of opposite charge.
- Electrode processes
- At the negative cathode positive ions gain electrons, and at the positive anode negative ions lose electrons, forming neutral atoms.
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