Metallic bonding

Key Definition Metallic bonding is the strong electrostatic attraction between positive metal ions arranged in a regular lattice and the delocalised electrons that surround them.

When metal atoms come together, their outer electrons become delocalised — free to move throughout the entire structure — leaving behind a lattice of cations. This bonding acts in all directions and holds millions of ions together, making metals giant structures. A 2-D diagram of the lattice shows regularly arranged positive ions with delocalised electrons filling all the spaces between them.

The nature of metallic bonding explains two important physical properties.

Electrical conductivity

• Metals conduct electricity because the delocalised electrons can flow through the structure when a voltage is applied, carrying charge as an electric current.

Malleability

• Metals are malleable because layers of ions can slide past one another without breaking the metallic bond — the delocalised electrons adjust to the new ion positions and continue to provide electrostatic attraction.

These properties distinguish metals from ionic solids, where the ions are locked in fixed positions and no delocalised electrons exist.