Metallic Bonding and Properties of Metals and Alloys — AQA GCSE Chemistry
Metallic bonding explains why metals conduct electricity, are malleable and have high melting points.
Metallic bonding
Metals consist of a giant structure of positive metal ions arranged in a regular lattice, surrounded by a "sea" of delocalised electrons (the outer electrons that are free to move). The strong electrostatic attraction between the positive ions and the delocalised electrons is the metallic bond.
Properties of metals
- High melting and boiling points — the metallic bonds are strong and need lots of energy to break.
- Good conductors of electricity and heat — the delocalised electrons are free to move and carry charge/energy.
- Malleable and ductile — the layers of ions can slide over each other when a force is applied.
Alloys
A pure metal is often too soft for many uses because its layers of identical atoms slide over each other easily.
An alloy is a mixture of a metal with one or more other elements (often other metals). The different-sized atoms distort the regular layers, making it harder for them to slide. This makes alloys harder than the pure metal.
Examples: steel (iron + carbon), bronze (copper + tin), brass (copper + zinc).
Exam tips
- Describe metallic bonding: positive ions + sea of delocalised electrons, held by electrostatic attraction.
- Explain conductivity (delocalised electrons carry charge) and malleability (layers slide).
- Alloys are harder because different-sized atoms distort the layers.
- Learn example alloys (steel, bronze, brass).