# Explain why magnesium oxide (MgO) has a higher melting point than sodium chloride (NaCl).

> IB DP Chemistry Standard Level (2023 syllabus) — S2.1 The ionic model · Explain · 4 marks

## Mark scheme (4 marks)

1. Both compounds are ionic, consisting of a lattice of oppositely charged ions held together by electrostatic attraction.
2. The ions in MgO carry charges of 2+ and 2−, whereas the ions in NaCl carry charges of only 1+ and 1−.
3. The greater charge on the ions in MgO results in a stronger electrostatic attraction between the ions.
4. More energy is therefore required to overcome these stronger electrostatic forces in MgO, so its melting point is higher.

## Key terms

- [melting point](https://www.gradenine.co.uk/glossary/melting-point)

## Related

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