1. Metal atoms release their OUTER ELECTRONS — these electrons become DELOCALISED, meaning they are free to move throughout the entire metal structure.
2. The metal atoms become POSITIVE IONS (they've lost electrons).
3. The positive metal ions are arranged in a regular LATTICE structure.
4. The DELOCALISED ELECTRONS move freely between and around the positive ions — forming a 'SEA OF ELECTRONS'.
5. STRONG ELECTROSTATIC ATTRACTION between the positive ions and the negative electron sea holds the metal together — THIS IS THE METALLIC BOND.
This model is sometimes called the 'electron sea model' — you can picture metal ions floating in a sea of freely moving electrons.
Properties Explained by Metallic Bonding
The metallic bonding model explains ALL key metal properties:
HIGH MELTING AND BOILING POINTS:
Strong electrostatic forces between many positive ions and the electron sea.
A lot of energy needed to overcome these forces.
Tungsten (W): melts at 3422°C — one of the highest melting metals.
GOOD ELECTRICAL CONDUCTORS:
Delocalised electrons can move freely through the structure.
When a voltage is applied, electrons flow — carrying charge.
GOOD THERMAL CONDUCTORS:
Delocalised electrons also carry thermal (heat) energy rapidly through the structure.
MALLEABLE (can be hammered into shapes):
Layers of positive ions can SLIDE past each other without breaking the metallic bond — the electron sea re-surrounds the ions in any new position.
DUCTILE (can be drawn into wires):
Same reason — ion layers slide without the structure breaking.
Alloys
ALLOYS are MIXTURES of metals (or a metal with a small amount of another element — sometimes carbon).
Why alloys are often harder and stronger than pure metals:
In a PURE METAL, all ions are the same size — layers of ions can slide over each other easily (making the metal soft and malleable).
In an ALLOY, different sized atoms are introduced — they DISRUPT the regular lattice.
The different-sized atoms prevent layers from sliding as easily → the alloy is HARDER and STRONGER than the pure metal.
Examples of alloys and their uses:
STEEL (iron + carbon) — harder than pure iron — used in construction, tools, cars.
BRONZE (copper + tin) — harder than pure copper — used in sculptures, coins, bearings.
BRASS (copper + zinc) — harder than pure copper — used in musical instruments, door fittings.
ALUMINIUM ALLOYS (aluminium + various elements) — strong and lightweight — used in aircraft.
⚠️ Common Mistake
The metallic bond is the attraction between POSITIVE METAL IONS and the SEA OF DELOCALISED ELECTRONS — not between individual atoms directly. Malleability works because ion LAYERS slide — the electron sea allows this without breaking bonds. If layers had to break ionic bonds (like in ionic compounds), the metal would shatter instead of bend.
📌 Key Note
Metallic bonding: positive metal ions in a lattice + sea of delocalised electrons. High MP/BP (strong electrostatic forces). Conducts electricity and heat (delocalised electrons move freely). Malleable/ductile (layers slide, electron sea remains). Alloys harder — different sized atoms disrupt regular lattice.