Metallic Bonding: Electron Sea Model (detailed) — free printable diagram

What the electron sea model shows

The electron sea model is the standard way of picturing metallic bonding. A metal is drawn as a regular lattice of positive metal ions sitting in a 'sea' of delocalised electrons — outer-shell electrons that have left their individual atoms and are free to move throughout the whole structure. The bond is the electrostatic attraction between those positive ions and the shared negative electrons.

Positive ions

Metal atoms that have lost their outer electrons

The 'sea'

Delocalised electrons, free to move through the structure

The bond

Attraction between positive ions and delocalised electrons

Arrangement

A regular, closely packed lattice

Explains

Electrical and thermal conductivity, malleability, high melting points

• 'Delocalised' is the key word: the electrons are not tied to any one atom and are shared across the entire lattice. That is what separates metallic bonding from covalent bonding, where a pair of electrons is shared between two specific atoms.
• Metals conduct electricity because the delocalised electrons are free to drift through the structure when a voltage is applied. The ions themselves stay where they are.
• The same free electrons carry energy quickly through the metal, which is why metals also conduct heat well.
• Metals are malleable and ductile because layers of ions can slide over one another without breaking the bonding — the electron sea simply flows with them and the attraction is maintained. In an ionic solid the same movement would push like charges together and shatter the crystal.
• Melting points are generally high because the attraction between the ions and the electron sea is strong and acts throughout the whole structure, so a large amount of energy is needed to break it down.
• The model is a simplification and is drawn in two dimensions, while a real metal lattice is three-dimensional and closely packed. It is a useful picture for explaining properties, not a literal photograph of the metal.