1.8 Metallic BondingEdexcel IGCSE Chemistry: Revision notes
Section 1
How is a metallic lattice represented?
A metallic structure can be represented by a simple 2-D diagram showing regular rows/layers of positively charged metal ions (drawn as circles with their charge, e.g. shown as a grid of positive circles) surrounded by a 'sea' of delocalised electrons filling the spaces between them.
The electrons shown are not attached to any one ion — they are free to move throughout the whole structure.
Section 2
What is metallic bonding?
In a metal, each atom's outer-shell electrons become delocalised — free to move throughout the whole structure — leaving behind a lattice of positively charged metal ions.
Metallic bonding is the strong electrostatic force of attraction between these positive metal ions and the sea of delocalised (negative) electrons surrounding them. This attraction acts throughout the whole structure, not just between neighbouring particles.
Always describe metallic bonding as an electrostatic attraction between positive ions and delocalised electrons — just saying 'electrons are shared' is a covalent-bonding description and won't score marks.
Section 3
How does metallic bonding explain the physical properties of metals?
| Property | Explanation |
|---|---|
| Good electrical conductivity | Delocalised electrons are free to move through the structure, carrying charge |
| Good thermal conductivity | Delocalised electrons transfer energy quickly through the structure |
| Malleable (can be hammered/bent into shape) | Layers of ions can slide over each other when force is applied, while the sea of delocalised electrons continues to hold the structure together as it changes shape |
| High melting/boiling point (generally) | Strong electrostatic attraction throughout the lattice requires a lot of energy to overcome |
Copper is used for electrical wiring because its delocalised electrons allow it to conduct electricity very well.
When explaining malleability, don't just say 'the ions can move' — explain that layers of ions slide over each other while the delocalised electrons keep attracting and holding the structure together, so it does not shatter like an ionic lattice would.
Must Know
- Metallic structure = a regular lattice of positive metal ions surrounded by a sea of delocalised electrons
- Metallic bonding is the strong electrostatic attraction between positive ions and delocalised electrons
- Delocalised electrons explain good electrical and thermal conductivity
- Malleability is explained by layers of ions sliding over each other while delocalised electrons continue to hold the structure together
- A 2-D diagram of a metal shows rows of positive ions with delocalised electrons filling the gaps
That's the notes covered.
Carry on to the next subtopic.