Aluminium is a metal widely used in overhead power cables and aircraft frames. Explain, in terms of metallic bonding, why aluminium is a good electrical conductor and why it has a high melting point.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Aluminium is a silvery-white metal. It is lightweight yet strong, and is chosen for electrical cables because it conducts electricity well. It has a melting point of 660 °C.
Model answer (5 marks)
Aluminium atoms lose their outer electrons to form positive ions (cations). The released electrons form a sea of delocalised electrons that can move freely throughout the structure. When a voltage is applied, the delocalised electrons can move towards the positive terminal, allowing charge (current) to flow. The positive ions and the delocalised electrons are held together by strong electrostatic forces of attraction. A large amount of energy is required to overcome these strong attractions, which is why aluminium has a high melting point.
Examiner tips
- Use the phrase 'sea of delocalised electrons' to show understanding of metallic bonding.
- Explain both conductivity and melting point in the same paragraph to show link between delocalised electrons and strong ion–electron attraction.
- Mention that the applied voltage drives the electrons, not the ions, for conductivity.
- Show the cause–effect chain: loss of electrons → delocalised sea → conductivity; strong ion–electron attraction → high melting point.
Common mistakes
- Confusing the movement of ions with electrons for electrical conduction.
- Omitting the term 'delocalised electrons' or 'sea of electrons'.
- Failing to link the strong electrostatic attraction to the high melting point.
Mark scheme (5 marks)
- Aluminium atoms lose their outer electrons to form positive ions (cations)
- The released electrons form a 'sea' of delocalised electrons that can move freely throughout the structure
- When a voltage is applied, the delocalised electrons can move towards the positive terminal, allowing charge (current) to flow
- There are strong electrostatic forces of attraction between the positive ions and the delocalised electrons
- A large amount of energy is needed to overcome these strong attractions, which is why aluminium has a high melting point
Key terms in this question
metallic bonding · electrical conductor
Related
- All Edexcel A-Level Chemistry (9CH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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