What Are Metals?
Metals are elements that occupy the left-hand side and centre (transition metals) of the periodic table. About 75% of all known elements are metals. At room temperature, all metals are solid except mercury (Hg), which is a liquid.
Common metals you may know include: iron (Fe), copper (Cu), aluminium (Al), gold (Au), silver (Ag), zinc (Zn), and sodium (Na).
Physical Properties of Metals
| Property | Explanation |
|---|---|
| Shiny (lustrous) | Reflect light from their smooth surfaces when polished |
| Good conductors of heat | Metal particles pass heat energy quickly |
| Good conductors of electricity | Free electrons carry electrical charge through the metal |
| Malleable | Can be hammered into flat sheets without breaking |
| Ductile | Can be drawn into thin wires |
| High melting and boiling points | Strong bonds between metal atoms need a lot of energy to break |
| High density | Atoms are closely packed |
The reason metals conduct electricity is that their outer electrons are not attached to any one atom — they float freely through the structure as a "sea of electrons". When a voltage is applied, these free electrons flow in one direction, carrying electrical current. This is also why metals conduct heat well: the free electrons carry kinetic energy quickly from hot areas to cooler ones.
Exceptions and Variations
Not all metals share every property equally:
- Mercury is liquid at room temperature (melting point: −39 °C).
- Sodium and potassium are soft enough to cut with a knife.
- Lead has a low melting point for a metal (327 °C).
- Tungsten has the highest melting point of all metals (3422 °C) and is used for light bulb filaments.
Chemical Properties of Metals
Most metals react with oxygen to form metal oxides (this is why iron rusts). Many react with dilute acids to produce a salt and hydrogen gas. The reactivity series ranks metals from most to least reactive:
Most reactive → Potassium, Sodium, Calcium, Magnesium, Aluminium, Zinc, Iron, Copper → Least reactive
Gold is so unreactive that it does not tarnish or corrode in air or water, which is why it is used in jewellery and electronic circuits.
Aluminium seems to contradict the reactivity series — it is quite high in the series, yet it does not corrode easily. This is because when aluminium is first exposed to air, it instantly forms a thin, hard layer of aluminium oxide on its surface, which protects the metal underneath.
Uses of Metals
| Metal | Property used | Common use |
|---|---|---|
| Copper | Conducts electricity, ductile | Electrical wires |
| Iron/Steel | Strong, malleable | Construction, vehicles |
| Aluminium | Lightweight, resistant to corrosion | Aircraft, food packaging |
| Gold | Unreactive, conducts electricity | Jewellery, computer circuits |
Real world: Copper wires in your home
Every electrical cable in your home is made of copper. Copper is chosen because it has free electrons that can carry charge easily (high conductivity) and it can be drawn into thin flexible wires (high ductility). It is also resistant to corrosion. Aluminium is used for long-distance power lines because it is lighter, despite being a slightly less good conductor.
Real world: Iron and steel in construction
Iron is extracted from iron ore in blast furnaces and then converted to steel (iron + small amounts of carbon). Steel combines iron's strength and malleability with improved hardness. It is used in building frames, bridges, car bodies, and kitchen appliances. The malleability of iron allows it to be shaped and welded into complex structures.
Real world: Gold in electronics
Gold is used in computer processors, smartphones, and high-quality connector pins. Despite being expensive, its extreme resistance to corrosion (it stays shiny and conductive indefinitely) and excellent electrical conductivity make it worth using in critical circuits. A tiny amount of gold in a laptop's CPU ensures reliable contact that does not degrade over years of use.
Where do you see this in real life? Look at electrical cables (copper), drink cans (aluminium), bridges (steel), coins (various metal alloys). Every metal was chosen for that use because of its specific metallic properties.
Practice Problems
Explain, in terms of electrons, why metals are good conductors of electricity.
Show answer
A student says copper and sodium are both metals, so they must have very similar properties. Give two ways they are different.