Describe metallic bonding
Model a metal as positive ions attracted to delocalised electrons, distinguishing the lattice from covalent and ionic structures.
Section 3 · Chemical bonding
AS Level; Cambridge International Chemistry 9701, 2025–2027 syllabus. Use the supplied Pauling values when given, show particle and bond reasoning, and distinguish intramolecular bonds from intermolecular forces. Written practice is self-checked
Before you begin
- Read element symbols and simple molecular formulae; use the Periodic Table.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which particles are attracted in metallic bonding?
What you will learn
- Define metallic bonding
- Describe positive metal ions and delocalised electrons in a metal
Metallic bonding is attraction between positive ions and mobile electrons
Metallic bonding is the electrostatic attraction between positive metal ions and delocalised electrons. The ions occupy a regular lattice; the delocalised electrons are not confined to one bond between two atoms.
A simplified model can account for electrical conduction: mobile electrons move through the structure when a potential difference is applied. This model does not mean the metal consists of isolated metal molecules.
Use the model to explain conduction
When a potential difference is applied, delocalised electrons can move through the metal lattice and carry charge. The positive ions remain in their ordered positions in the simplified solid-state model.
This explanation identifies the charge carriers and their motion; it does not require the positive ions to flow through the metal as a current.
Pause and explain
What does delocalised mean in the metallic model?
Worked example
Describe metallic bonding in copper.
Show the worked solution
- Copper atoms contribute outer electrons to a delocalised electron system.
- Positive copper ions remain arranged in a lattice.
- Electrostatic attraction between the positive ions and delocalised electrons holds the structure together.
Answer Metallic bonding is electrostatic attraction between positive metal ions and delocalised electrons in the lattice.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
State the definition of metallic bonding and identify the two particle types.
Give me a hint
Name both charge types before describing their attraction.
Compare my reasoning
- The lattice contains positive metal ions.
- Delocalised electrons occupy the metal structure.
- Opposite charges attract electrostatically.
Metallic bonding is electrostatic attraction between positive metal ions and delocalised electrons.
Look for these in your work
- Definition substantially correct
- Both particle types named
- Attraction identified
Use the metallic bonding model to explain why copper can conduct electricity.
Give me a hint
Relate the applied potential difference to the mobile particles.
Compare my reasoning
- Copper contains delocalised electrons.
- These electrons can move through the lattice.
- Their directed movement carries charge.
Delocalised electrons move through copper when a potential difference is applied, carrying electrical charge.
Look for these in your work
- Delocalised electrons named
- Mobility explained
- Charge transport linked
A diagram shows fixed positive ions surrounded by mobile electrons. Identify the structure and explain why the mobile electrons are not covalent bonds.
Give me a hint
Ask whether each electron pair is confined between two named atoms.
Compare my reasoning
- The positive ions and mobile electron system indicate a metal.
- The electrons are delocalised through the structure.
- A covalent bond is a localised shared pair between two nuclei.
It represents metallic bonding. The electrons are delocalised, not a localised shared pair between two particular atoms as in a covalent bond.
Look for these in your work
- Metallic model recognised
- Delocalised property stated
- Covalent contrast accurate
Common mistakes
- Calling the mobile electrons covalent shared pairs
- Describing metallic bonding as attraction between neutral atoms
- Treating the metal as separate molecules
What can you explain now?
Which particles are attracted in metallic bonding?
Compare with the explanation
Positive metal ions and delocalised electrons
These opposite charges form the metallic bond.
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Make it stick
Which two species form metallic bonding, and which one can move through the metal?
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