Tungsten is a metal used to make the filaments of incandescent light bulbs because it has a very high melting point and can be drawn into thin wires. Tungsten has a giant metallic structure. Describe the structure of a giant metallic structure and use this structure to explain why tungsten can be drawn into thin wires without breaking.

Pearson Edexcel International GCSE Chemistry (4CH1) — 1.8 Metallic crystals · Describe · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Tungsten has one of the highest melting points of any metal (3422 °C) and is used to make the thin filaments found inside incandescent light bulbs.

Model answer (4 marks)

A giant metallic structure consists of a regular lattice of positive ions surrounded by a sea of delocalised electrons.
When a force is applied, layers of positive ions can slide over one another.
The delocalised electrons move with the ions, maintaining the metallic bonding, so the structure does not break.

Examiner tips

  • Use the phrase "regular lattice of positive ions" and "sea of delocalised electrons". Show that ion layers can slide to explain ductility. Mention that electrons keep the ions bonded while sliding.

Common mistakes

  • Confusing the lattice with a crystal structure of a covalent or ionic solid. Forgetting to mention the delocalised electrons. Saying the metal breaks instead of explaining ductility.

Mark scheme (4 marks)

  1. A giant metallic structure consists of a regular lattice of positive ions (cations)
  2. Surrounded by / with a sea of delocalised electrons
  3. When a force is applied, layers of positive ions can slide / move over one another
  4. The delocalised electrons move with the ions, maintaining the metallic bonding / electrostatic attraction, so the structure does not break

Key terms in this question

giant metallic structure

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