Metallic bonding
Metals are made up of positive metal ions in a regular lattice, surrounded by a "sea" of delocalised outer electrons. The electrostatic attraction between the positive ions and this sea is the metallic bond.
Why this structure?
Metal atoms readily lose their outer electrons. Once free, the electrons no longer belong to a single atom — they roam through the structure, holding everything together.
Properties explained
| Property | Explanation |
|---|---|
| Good electrical conductor | Delocalised electrons can move and carry charge |
| Good thermal conductor | Delocalised electrons transfer kinetic energy quickly |
| Malleable / ductile | Layers of ions can slide over each other while the sea of electrons keeps them bonded |
| High melting points | Strong electrostatic attraction between ions and electrons needs lots of energy to overcome |
| Shiny when polished | Delocalised electrons reflect light at the surface |
Alloys
A pure metal is too soft for many uses because its identical-sized atoms slide over each other easily. An alloy is a mixture of a metal with one or more other elements (often another metal). The different-sized atoms disrupt the regular lattice, so layers can no longer slide past each other as easily — the alloy is harder than the pure metal.
| Alloy | Composition | Use |
|---|---|---|
| Steel | Iron + carbon | Bridges, cars, tools |
| Stainless steel | Iron + chromium + nickel | Cutlery, surgical instruments |
| Brass | Copper + zinc | Door handles, instruments |
| Bronze | Copper + tin | Statues, bells |
| Solder | Tin + lead (now lead-free) | Joining metal components |
WJEC exam tip
Two killer phrases for full marks: (1) "delocalised electrons" — never just "free electrons"; (2) "different-sized atoms disrupt the regular layers". Use both in any alloy or metallic-bonding answer and you cover the highest-mark response.
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