Alloys

An alloy is a mixture of a metal with other elements. For example, brass contains copper and zinc. Stainless steel contains iron and other elements, including chromium, nickel and carbon.

Recognising an alloy in a structural diagram

A diagram of a pure metal shows only one type of atom in a regular arrangement. A diagram of an alloy shows different types of atoms mixed within the metallic structure. These may be represented by circles of different sizes or colours.

Why alloys can be harder and stronger

In a pure metal, the regular arrangement allows layers of atoms to slide past one another relatively easily. In an alloy, atoms of different sizes can disrupt this arrangement, making it harder for the layers to slide. Alloys can therefore be harder and stronger than pure metals, making them more useful for some purposes.

Stainless steel is used for cutlery because it is hard and resists rusting.