Metallic Bonding
Principles of Chemistry · 2 question types
Exam Frequency Analysis
Past paper frequency (2018 to 2024)
This topic accounts for approximately 5% of your exam marks.
Shorter-answer topic; typically tested alongside ionic and covalent bonding comparisons.
What an alloy is
- An alloy is a mixture of a metal with one or more other elements (usually another metal, sometimes a non-metal such as carbon)
- Common examples:
- Steel: iron with a small percentage of carbon
- Brass: copper and zinc
- Bronze: copper and tin
Why alloys are harder than the pure metal
- The added element has atoms of a different size from the host metal
- These differently sized atoms disrupt the regular arrangement of the lattice
- The layers can no longer slide smoothly past each other
- The alloy is therefore harder and stronger, with reduced malleability compared with the pure metal
Why an alloy is harder than the pure metal
What comes up: "Explain why an alloy is harder than the pure metal" or "explain why the alloy is stronger than the pure metal" (2–3 marks).
Write (three marks): (1) In the pure metal, the layers of atoms/ions are regular and can slide over each other easily. (2) The differently sized atoms in the alloy disrupt this regular arrangement. (3) This makes it harder for the layers to slide, so the alloy resists deformation.
Watch out: The mark scheme deducts a mark if layers/sheets/rows are not mentioned at all. It also rejects molecules, intermolecular forces, negative ions, and ionic or covalent bonding — use ions, atoms, or particles throughout.