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Cambridge O Level Chemistry 5070 — 2.7 Metallic Bonding — Cambridge O Level Chemistry 5070 Revision Notes & Topical Questions

5 min read 5 parts Lesson 7 of 7

📚 Cambridge O Level Chemistry 5070 Hub / Topical Revision
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Lesson summary

2.7 Metallic Bonding — Cambridge O Level Chemistry: describe the giant metallic lattice and use its structure to explain melting point, electrical conductivity and malleability. Giant latticeIn a solid metal, atoms form a regular, repeating three-dimensional arrangement.

  • The metallic bond
  • Exam explanation
  • Compare with an ionic solid
  • Worked example

Part 1 of 5Structure of a metal

Structure of a metal
Giant lattice
In a solid metal, atoms form a regular, repeating three-dimensional arrangement. Their outer electrons become delocalised: they are no longer attached to one particular atom and can move through the lattice. The atoms left behind are positive metal ions.
The metallic bond
Metallic bonding is the strong electrostatic attraction between positive metal ions and the negatively charged delocalised electrons. This attraction holds the giant lattice together. A metal alloy also has metallic bonding, although it contains more than one type of atom.

Part 2 of 5Melting and boiling

Most metals have relatively high melting and boiling points because a large amount of energy is needed to overcome the strong attraction between the positive ions and delocalised electrons throughout the lattice.
  • The exact temperature varies between metals because the strength of metallic bonding varies.
Exam explanation
When asked why a metal has a high melting point, name both the positive metal ions and the delocalised electrons, state that the attraction between them is strong, and link that strength to the large energy input needed.

Part 3 of 5Electrical conductivity

1
Metals conduct electricity as solids because their delocalised electrons can move through the lattice. When a potential difference is applied, the electrons carry electrical charge. The ions stay in their lattice positions; they are not the mobile charge carriers in solid metal.
2Compare with an ionic solid
An ionic solid does not conduct while solid because its charged ions cannot move freely. A metal can conduct while solid because it has mobile electrons. This distinction helps identify which particles carry the charge.

Part 4 of 5Malleability

Metals are malleable, so they can be hammered or rolled into sheets, and ductile, so they can be drawn into wires.
  • The positive metal ions form layers that can slide past one another.
  • The delocalised electrons move with the layers and continue to attract the ions,
  • so the metallic bonding is maintained as the metal changes shape.
Worked example
Explain why copper can be drawn into a wire and still conduct electricity. Its ion layers can change position while mobile delocalised electrons keep the lattice bonded and carry charge through the wire. In contrast, an ionic solid has no mobile charge carriers until it melts or dissolves.

Part 5 of 5Check your understanding

    • 1.
    • Define a delocalised electron.
    • 2.
    • Identify the two types of charged particle involved in metallic bonding.
    • 3.
    • Explain why a metal conducts electricity when solid.
    • 4.
    • Use the lattice model to explain malleability.
    • 5.
    • Explain a high melting point in terms of force and energy.

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