Alloys — Metallic Bonding | IGCSE Chemistry

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 5% of your exam marks.

stable

Rare

Stable5%

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

Exam tip

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.