Metals and Alloys

In this chapter you will learn:

Properties of Metals

Metals are good conductors of thermal energy because energy is transferred through the delocalised electrons.
Metals have high density and very high melting and boiling points.
Metals are also malleable.
Metals are good conductor of heat due to the delocalised electrons..
Metallic bonds are very strong and a result of the attraction between the positive metal ions and the negative delocalised electrons.
In pure metals, atoms are arranged in layers, which allows metals to be bent and shaped without breaking the bonds. When a force is applied, the layers may slide over each other.
Pure metals are too soft for many uses and so are mixed with other metals to make alloys which are harder.
The layers of atoms in pure metals can slide over each other.

Alloys are mixtures of metals.
Bronze is an alloy of copper and tin.
Brass is an alloy of copper and zinc.
Gold is an alloy with silver, copper and zinc.
Steels are alloys of iron that contain specific amounts of carbon and other metals.
Alloys can be made from metals mixed with nonmetals such as carbon.
Alloys are usually much harder than the pure metal.
Alloys contain atoms of different sizes. This makes difficult for the layers to slide over each other.

Alloys are used to make dental braces and coins. Nitinol is an alloy used in dental braces because the alloy is able to return its original shape.