Magnesium oxide is an ionic compound used as a lining in furnaces that operate at very high temperatures. Explain why magnesium oxide is suitable for this use, in terms of its structure and bonding.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Magnesium oxide is formed when magnesium atoms lose two electrons to oxygen atoms. It is used to line industrial furnaces because it can withstand extremely high temperatures without melting.
Model answer (5 marks)
Magnesium oxide is an ionic compound.
1. Mg atoms lose two electrons to form Mg²⁺ ions, while O atoms gain two electrons to form O²⁻ ions.
2. The oppositely charged ions attract strongly via electrostatic forces.
3. The ions are arranged in a giant lattice, giving the compound a three‑dimensional structure.
4. The lattice requires a large amount of energy to break the strong ionic bonds.
5. Consequently, MgO has a very high melting point and can withstand the high temperatures of industrial furnaces.
1. Mg atoms lose two electrons to form Mg²⁺ ions, while O atoms gain two electrons to form O²⁻ ions.
2. The oppositely charged ions attract strongly via electrostatic forces.
3. The ions are arranged in a giant lattice, giving the compound a three‑dimensional structure.
4. The lattice requires a large amount of energy to break the strong ionic bonds.
5. Consequently, MgO has a very high melting point and can withstand the high temperatures of industrial furnaces.
Examiner tips
- Use the word "ionic" and mention ions explicitly. State the charges Mg²⁺ and O²⁻. Explain the lattice and strong electrostatic attraction. Link the high lattice energy to the high melting point.
- Keep each point brief and to the point – examiners look for concise, accurate statements.
Common mistakes
- Failing to mention the charges of the ions. Using “covalent” or “metallic” instead of “ionic”. Not linking lattice energy to high melting point.
Mark scheme (5 marks)
- Magnesium oxide is an ionic compound / contains ions
- Magnesium forms a positive ion and oxygen forms a negative ion (or Mg²⁺ and O²⁻ stated)
- There are strong electrostatic forces of attraction between the oppositely charged ions
- Magnesium oxide has a giant ionic structure / the ions are arranged in a lattice
- A large amount of energy is needed to break these strong electrostatic forces, so magnesium oxide has a very high melting point / is suitable for use at very high temperatures
Key terms in this question
Related
- All OCR A-Level Chemistry A (H432) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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