A level Chemistry · Edexcel 9CH0 · Topic 2F
Metallic bonding and structure
Key points
- Metallic bonding is the electrostatic attraction between a lattice of positive metal ions and a sea of delocalised electrons.
- Strength rises with more delocalised electrons per atom and smaller ions, so Mg has a higher melting point than Na.
- Metals conduct electricity because delocalised electrons move; they are malleable because layers of ions slide without breaking the bonding.
- Giant covalent structures (diamond, graphite, silicon, SiO₂) have very high melting points because many strong covalent bonds must break.
- Graphite conducts (one delocalised electron per carbon) and is soft (weak forces between layers); graphene is a single layer.
- Simple molecular substances (I₂, ice, P₄) have low melting points because only weak intermolecular forces break.
- Be able to predict structure type from data on melting point, conductivity and solubility.
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Metals owe their conductivity and malleability to a sea of delocalised electrons. This sub-topic also pulls together the four types of structure, so you can predict properties from structure and work backwards from properties to structure.
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