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# Metals and alloys

## What is an alloy?

An alloy is a metal that is a mixture containing a metal and at least one other element. This other element could be another metal or a non-metal. Alloys are commonly used in everyday materials.

A die made of brass placed next to its components, copper $(\ce{Cu})$ and zinc $(\ce{Zn})$

The following table lists some common alloys and their components.

Alloy Elements involved Applications
Bronze Copper $(\ce{Cu})$, Tin $(\ce{Sn})$ Sculptures, statues
Brass Copper $(\ce{Cu})$, Zinc $(\ce{Zn})$ Musical instruments (e.g. trombone, trumpet)
Lead solder Tin $(\ce{Sn})$, Lead $(\ce{Pb})$ Used to fuse metals in electronics
Steel Iron $(\ce{Fe})$, Carbon $(\ce{C})$ Cutlery, structural support in buildings

## Alloy properties

Alloys tend to be harder and less malleable than elemental metals.

In metals, the planes of atoms can easily slide past each other. In alloys, planes do not slide as easily because there are different atoms in the structure.

Atoms of different elements have different sizes. The presence of atoms of different sizes disrupts the orderly arrangement that is usually present in pure metals. This makes the sliding of planes difficult.

Alloys are therefore usually harder, stiffer and more brittle. These are desirable properties where a degree of stiffness is needed, e.g. in buildings and machinery.

Bronze has copper and tin atoms. The tin atoms are almost twice as big as the copper atoms. These planes cannot slide easily. Bronze is harder than pure copper and tin.