A lattice of positive ions in a sea of shared electrons — the picture that explains why metals conduct, bend and stay solid at high temperatures.
Theme · StructureStructure 2.3
This is the Standard Level lesson, covering S2.3.1–S2.3.2. Taking Chemistry at Higher Level? The HL version adds the transition elements — why their delocalised d-electrons give them such high melting points.
👆 Switch on the current in the model · click each property · compare the metals
1. The electron-sea model S2.3.1
In a metal, each atom loses its outer electrons to become a positive cation. Those electrons are no longer attached to any one atom — they are delocalised, free to move through the whole structure as a "sea". The metallic bond is the electrostatic attraction between the fixed lattice of cations and this sea of delocalised electrons. Press Apply voltage and watch the free electrons drift — that flow is an electric current.
Animated electron-sea model
Random: the delocalised electrons move in all directions between the fixed metal cations.
2. Why metals behave as they do S2.3.1
Every classic property of a metal comes straight from the electron-sea model. Click each:
3. How strong is the metallic bond? S2.3.2
The strength of metallic bonding — and so the melting point — increases with the charge of the cation, a smaller ionic radius, and more delocalised electrons per atom. Compare three period-3 metals:
Melting points of period-3 metals
Click a barNa → Mg → Al: the cation charge rises 1+ → 2+ → 3+ and each atom releases more delocalised electrons, so the metallic bond gets stronger and the melting point rises.
Going to HL? The HL lesson adds the transition elements: they also delocalise d-electrons, giving many more electrons in the sea and unusually strong metallic bonding — which is why iron, titanium and tungsten have such high melting points. → Open the HL version
Common mistakes examiners see
What is a metallic bond?✗ The sharing of electrons between two metal atoms.✓ The electrostatic attraction between a lattice of positive cations and a sea of delocalised electrons.
Why can metals be bent and shaped (malleable)?✗ The bonds break and reform as new bonds.✓ Layers of cations slide over one another while the delocalised electrons keep holding everything together, so the metal deforms without shattering.
Why does aluminium have a higher melting point than sodium?✗ Aluminium atoms are heavier.✓ Al³⁺ has a higher charge, a smaller radius and 3 delocalised electrons per atom (vs 1 for Na⁺), so the metallic bond is much stronger.
Why do metals conduct electricity?✗ The cations move and carry charge.✓ The delocalised electrons are free to move and carry the charge; the cations stay fixed in the lattice.