Explain why magnesium has a high melting point and conducts electricity.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Magnesium is a metal used in lightweight alloys for aircraft and sports equipment. It is a solid at room temperature and is a good electrical conductor.
Model answer (4 marks)
Magnesium has a giant metallic structure, meaning the atoms form a lattice of positive ions surrounded by a sea of delocalised electrons. The electrostatic attraction between the ions and the delocalised electrons is very strong, so a large amount of energy is required to break these forces and melt the metal. This gives magnesium a high melting point.
Because the electrons are delocalised, they can move freely through the lattice. When a potential difference is applied, these free electrons carry charge through the metal, allowing it to conduct electricity.
Because the electrons are delocalised, they can move freely through the lattice. When a potential difference is applied, these free electrons carry charge through the metal, allowing it to conduct electricity.
Examiner tips
- Use the phrase "giant metallic structure" to show understanding of the lattice. Explain the role of delocalised electrons in both melting point and conductivity. Link the strong electrostatic forces to the high melting point. Mention that free electrons carry charge for electrical conduction.
Common mistakes
- Confusing the melting point with boiling point. Forgetting to mention the delocalised electrons or the lattice structure. Using vague terms like "metallic bonding" without explaining the lattice or electron movement.
Mark scheme (4 marks)
- Magnesium has a giant metallic structure / lattice
- 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 forces, hence the high melting point
- Delocalised electrons are free to move through the structure and carry charge, allowing electrical conduction
Related
- All Edexcel GCSE Chemistry (1CH0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Types of substance questions
- Explain why sodium chloride has a high melting point but does not conduct electr…
- Explain why graphite can conduct electricity but diamond cannot, even though bot…
- Explain why silicon dioxide has a high melting point and does not conduct electr…
- Explain why iodine has a low melting point and does not conduct electricity.