Metals and non-metals
Metals and non-metals have different properties. Properties of metals can be explained in terms of metallic structure and bonding. Different chemical models have different features and limitations.
Metals vs non-metals
Metals are placed on the left-hand side of the periodic table, and non-metals on the right.
Physical properties
The table summarises some typical properties of metals and non-metals.
| Metals | Non-metals |
|---|---|
| Shiny | Dull |
| High melting points | Low melting points |
| Good conductors of electricity | Poor conductors of electricity |
| Good conductors of heat | Poor conductors of heat |
| High density | Low density |
| Malleable | Brittle |
Some elements have properties that are not typical. For example:
- mercury (a metal) has a low melting point and exists as a liquid at room temperature
- graphite, a form of carbon (a non-metal), has a high boiling point and is also a good conductor of electricity
A substance with a high density means it has a high mass for its size.
Malleable substances can be bent or hammered into shape without shattering, while brittle substances shatter when bent or hit.
Ductile means that a substance can be drawn out into a long wire without snapping or breaking.
Metallic structure and bonding
In metals, the electrons leave the outer shells of metal atoms, forming positive metal ions and a 'sea' of delocalised electrons. The structure of a solid metal consists of closely packed metal ions, arranged in a regular way to form a metallic lattice structure.
Metallic bonding is the strong electrostatic force of attraction between the metal ions and the delocalised electrons.
Explaining metal properties
Malleability
Metals are malleable because layers of ions can slide over each other when a force is applied. Metallic bonding allows the metal to change shape without shattering.
Conduction of electricity
When a voltage is applied to a metal, the delocalised electrons travel through the lattice structure. The movement of these charged particles forms an electric current.