Explain why magnesium oxide is held together by strong electrostatic forces and why these forces act in every direction.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Magnesium oxide is an ionic compound formed when magnesium, a Group 2 metal, reacts with oxygen, a Group 6 non-metal.
Model answer (4 marks)
Magnesium atoms lose two electrons to form Mg²⁺ ions, while oxygen atoms gain two electrons to form O²⁻ ions.
The oppositely charged Mg²⁺ and O²⁻ ions attract each other, creating strong electrostatic forces.
These ions arrange themselves into a giant ionic lattice.
In the lattice each ion is surrounded by oppositely charged ions in all three dimensions, so the electrostatic forces act in every direction.
The oppositely charged Mg²⁺ and O²⁻ ions attract each other, creating strong electrostatic forces.
These ions arrange themselves into a giant ionic lattice.
In the lattice each ion is surrounded by oppositely charged ions in all three dimensions, so the electrostatic forces act in every direction.
Examiner tips
- Show the electron transfer step first to justify ion formation.
- Mention the attraction between opposite charges to explain the force.
- Explain the giant lattice structure to justify the three‑dimensional arrangement.
- Use the phrase ‘electrostatic forces act in every direction’ to hit the last point.
Mark scheme (4 marks)
- Magnesium atoms lose two electrons to form Mg²⁺ ions (and oxygen atoms gain two electrons to form O²⁻ ions)
- The oppositely charged ions (Mg²⁺ and O²⁻) attract each other / electrostatic forces exist between oppositely charged ions
- Magnesium oxide forms a giant ionic lattice / giant structure of ions
- Each ion is surrounded by oppositely charged ions in three dimensions, so the electrostatic forces act in every direction
Key terms in this question
Related
- All AQA GCSE Chemistry (8462) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →