# Explain why most metals have high densities and why alloying a metal with another element can make it harder than the pure metal.

> Cambridge International IGCSE Chemistry (0620) — 2.7 Metallic bonding · Explain · 4 marks

## Mark scheme (4 marks)

1. Metal atoms/ions are closely packed together (in a regular arrangement/lattice)
2. This close packing means a large mass occupies a small volume, giving high density
3. In an alloy, atoms/ions of different sizes are introduced into the lattice
4. The differently sized atoms prevent layers of atoms from sliding over one another, so the alloy is harder/less malleable than the pure metal

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Chemistry (0620)](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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