# Explain why metals have high melting points and why the melting point of a metal generally increases across Period 3 from sodium to aluminium.

> IB DP Chemistry Standard Level (2023 syllabus) — S2.3 The metallic model · Explain · 4 marks

## Mark scheme (4 marks)

1. In metals, positive ions (cations/kernels) are surrounded by a 'sea' of delocalised electrons, and the metallic bond is the electrostatic attraction between these positive ions and the delocalised electrons.
2. To melt a metal, sufficient energy must be supplied to overcome these electrostatic attractive forces, so metals generally have high melting points.
3. Going from Na to Al across Period 3, the number of delocalised electrons per atom increases (Na provides 1, Mg provides 2, Al provides 3).
4. More delocalised electrons (and a higher ionic charge) result in stronger electrostatic attraction between the ions and the electron sea, so more energy is required to separate the ions and the melting point increases.

## Key terms

- [melting point](https://www.gradenine.co.uk/glossary/melting-point)
- [Period 3](https://www.gradenine.co.uk/glossary/period-3)

## Related

- [Revision notes for IB DP Chemistry Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-metals-have-high-melting-194d9fb3) · Published by Druglandscape Ltd.