Metallic bonding
CIE A-Level Chemistry· Unit 3: Chemical bonding· 10 min read
1. The Electron Sea Model of Metallic Bonding★☆☆☆☆⏱ 3 min
Metallic bonding occurs in pure metal elements and alloys. It is fundamentally different from ionic and covalent bonding because it is non-directional, meaning attraction acts equally in all directions throughout the giant lattice structure.
Metallic Bonding
The strong electrostatic force of attraction between closely packed positive metal cations and a surrounding sea of delocalised outer electrons that are not bound to any single atom.
Example:
In solid sodium, each Na atom loses its single outer electron to form a Na+ cation, which is fixed in a regular lattice surrounded by a sea of mobile delocalised electrons.
Describe the structure of pure metallic copper.
- 1
Pure copper has a giant metallic lattice structure, made up of positively charged Cu²⁺ ions arranged in a regular, repeating 3D pattern.
- 2
The outer electrons from each copper atom are delocalised, forming a 'sea' of mobile negative charge that fills the spaces between the positive cations.
- 3
The metallic bond is the strong electrostatic attraction between the positive Cu²⁺ ions and the negative delocalised electron sea.
Exam tip:
Always explicitly mention electrostatic attraction in your definition of metallic bonding — you will lose a mark if you only state attraction between ions and electrons.
2. Physical Properties of Metals Explained by Bonding
Explain why copper is ductile can be drawn into wires, while sodium chloride (an ionic solid) is brittle and cannot.
- 1
Copper has a giant metallic structure with non-directional metallic bonding between Cu²⁺ cations and delocalised electrons.
- 2
When a force is applied to draw copper into a wire, layers of Cu²⁺ cations slide past each other, but the electrostatic attraction between cations and the electron sea is maintained. The structure does not break.
text_section renderer not yet implemented · content will appear once shipped]4. Frequently Asked
Why do metals conduct electricity when solid?
Metals have delocalised free electrons that can move freely through the fixed lattice of positive ions to carry charge when a potential difference is applied, unlike ionic compounds that only conduct when molten or dissolved.
Why does magnesium have a higher melting point than sodium?
Magnesium forms 2+ cations compared to sodium's 1+ cations, has twice as many delocalised electrons per atom, and has a smaller ionic radius. This creates stronger electrostatic attraction between cations and the electron sea, requiring more energy to break bonds.
When this came up on past exams
AI-estimated based on syllabus patterns — cross-check with official past papers for accuracy. Use only as revision-focus signals.
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Structure of metallic bonding
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Melting point trend of metals
- 2021 · 1
Properties linked to bonding