Ductile – IGCSE Chemistry Definition and Key Facts

Ductility is a physical property of metals that appears in the Cambridge 0620 syllabus under metallic bonding and the properties of metals. It is closely linked to malleability — both properties arise from the same structural feature of metals.

The 0620 definition

A ductile material can be drawn out into a thin wire without breaking. Copper, gold, and aluminium are particularly ductile metals. Copper’s ductility makes it the standard material for electrical wiring in homes and electronics.

Explaining ductility using metallic bonding

In a metal, positive ions are arranged in regular layers. These ions are surrounded by a “sea” of delocalised electrons. When a pulling (tensile) force is applied:

1. Layers of metal ions slide over one another
2. The delocalised electrons shift with the ions, maintaining the attractive forces throughout the structure
3. The metallic bond is not broken — it simply reforms in the new position
4. The metal stretches into a wire instead of snapping

This explanation earns full marks on Paper 4 when candidates mention: layers sliding, delocalised electrons, and the metallic bond not breaking.

Ductile vs malleable

Property	Meaning	Force applied
Ductile	Can be drawn into wire	Tensile (pulling/stretching)
Malleable	Can be hammered into shape	Compressive (hammering/pressing)

Both properties come from layers of ions sliding over each other while the sea of delocalised electrons keeps them bonded. Many candidates confuse the two — remember, ductile = drawn into wire.

Ductility of different metals

Metal	Ductility	Use exploiting ductility
Copper	Very high	Electrical wiring
Gold	Very high	Thin gold wire in electronics
Aluminium	High	Overhead power cables
Iron/steel	Moderate	Wire rope, springs
Tungsten	High	Filament wire in light bulbs

Why alloys are less ductile

In a pure metal, all atoms are the same size and pack in a regular arrangement. Layers slide easily. In an alloy, atoms of a different element (different size) are mixed in. These differently-sized atoms disrupt the regular layering, making it harder for layers to slide. The alloy is typically harder and stronger but less ductile.

For example, brass (copper + zinc) is harder than pure copper and does not draw into wire as easily. Steel (iron + carbon) is much harder than pure iron.

Ductility and non-metals

Non-metals are generally not ductile. Ionic compounds are brittle — when a force moves the layers, ions of the same charge come next to each other and repel, causing the structure to shatter. Giant covalent structures are also not ductile because their strong covalent bonds hold atoms rigidly in place and cannot be rearranged by sliding.

Worked exam question

Copper is used for electrical wiring. (a) State the property of copper that allows it to be pulled into thin wires. [1] (b) Explain this property in terms of the structure and bonding in copper. [3]

(a) Ductility / copper is ductile [1]

(b) Copper has layers of positive ions [1]; surrounded by a sea of delocalised electrons [1]; when pulled, layers slide over each other and the metallic bond is maintained because the delocalised electrons move with the ions [1].

Common exam mistakes

1. Using the word “malleable” when the question asks about drawing into wires — the correct term is ductile.
2. Saying “atoms can slide” without mentioning that it is the delocalised electrons that maintain the bonding as the layers move.
3. Writing that metals are ductile because they are “soft” — ductility is about the ability to be drawn into wire, not about being soft.