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1.8.1States of Matter

Metallic Bonding — Cambridge IGCSE Chemistry 0620 Revision Notes & Topical Questions

5 min read 4 parts Lesson 19 of 30 Unit quiz

📚 Cambridge IGCSE Chemistry 0620 Hub / Topical Revision
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Part 1 of 4The Metallic Bond

1.8.1 Metallic Bonding

The outer electrons of metal atoms are not held by any single atom.

Metal lattice
  • A giant regular arrangement of positive metal ions packed in layers, rather than separate molecules.
Delocalised electrons
  • Outer electrons released by the metal atoms that move freely through the structure instead of belonging to one atom.
Metallic bond
  • The strong electrostatic attraction between the positive metal ions and the surrounding delocalised electrons.
Sea of electrons
  • A model in which delocalised electrons move between the positive ions and hold the whole structure together.

Part 2 of 4Properties Explained

Properties Explained
High melting point
  • The strong attraction between ions and electrons needs a large amount of energy to overcome,
    • so most metals melt at high temperatures.
Electrical conduction
  • Delocalised electrons move through the structure and carry charge when a potential difference is applied across the metal.
Malleability
  • Layers of ions slide over each other when hammered,
    • because the metallic bond is not fixed in one direction,
    • so the metal changes shape without breaking.
Thermal conduction
  • Delocalised electrons transfer thermal energy quickly through the metal, which is why metals conduct heat well.

Part 3 of 4Alloys

1
An alloy is a mixture of a metal with another element, usually another metal or carbon, combined to give better properties.
2
Atoms of different sizes in an alloy distort the regular layers of the metal lattice.
3
The distorted layers find it harder to slide over one another, so the alloy is harder and stronger than the pure metal.
4
Alloys often resist corrosion or extreme temperatures better than pure metals, which makes them more useful in practice.
AlloyMade fromTypical use
Mild steelIron with about 0.25% carbonCar body panels and wiring
High carbon steelIron with 0.5 to 1.4% carbonTools such as chisels
BrassCopper with about 30% zincDecorative items and fittings
Stainless steelIron with chromium and nickelCutlery, sinks and chemical plant

Part 4 of 4Exam Checklist & Tips

1.8.1 – Key Points for the Exam

  • Metallic bond The electrostatic attraction between positive metal ions and delocalised electrons.
  • Delocalised electron An electron that is free to move through the metal lattice.
  • Malleable Able to be hammered or pressed into shape without breaking.
  • Alloy A mixture of a metal with another element, designed to have improved properties.
  • Metal lattice The regular arrangement of positive metal ions in a metal.

Common Mistakes

  • Saying the lattice is made of metal atoms; in a metal the lattice is made of positive metal ions.
  • Describing the metallic bond as electrons shared between two specific atoms.
  • Explaining malleability by bonds breaking; the layers slide while the metallic bonding stays in place.
  • Using the word particles when explaining malleability; name the atoms or ions in the layers.

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