# Iron is a metal with a giant metallic structure. It is used to make steel railway tracks because of its high melting point and strength. Explain, in terms of structure and bonding, why iron has a high melting point and why it is able to be bent into shape without shattering.

> Pearson Edexcel International GCSE Chemistry (4CH1) — 1.8 Metallic crystals · Explain · 4 marks

> Iron has a giant metallic structure consisting of a lattice of positive ions surrounded by a sea of delocalised electrons. Railway engineers value iron-based metals for their ability to withstand high temperatures and to be shaped without cracking.

## Mark scheme (4 marks)

1. Iron consists of a lattice of positive ions surrounded by delocalised (free) electrons
2. There are strong electrostatic forces of attraction between the positive ions and the delocalised electrons
3. A large amount of energy is needed to overcome these strong forces / bonds, so the melting point is high
4. The layers of positive ions can slide over one another (without breaking the metallic bonding / whilst the delocalised electrons maintain the structure), so the metal can be bent without shattering

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel International GCSE Chemistry (4CH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/iron-is-a-metal-with-a-9b0be92b) · Published by Druglandscape Ltd.