Metallic bonding — AQA GCSE Combined Science
Test yourself on Metallic bonding with AQA GCSE practice questions.
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Metallic bonding explained
In a metal, vast numbers of identical atoms are packed together in a giant structure.
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The atoms are arranged in a regular, repeating pattern called a lattice, rather than as separate molecules. Each metal atom contributes its outer-shell electrons to a shared pool of delocalised electrons, while the remaining positive ions sit in fixed lattice positions. This arrangement explains typical metallic properties: the layers of ions can slide when the metal is deformed, and the delocalised electrons can move through the structure to carry charge and thermal energy. For example, copper consists of a regular lattice of Cu⁺ ions surrounded by delocalised electrons. The regular pattern extends throughout the piece of metal, so a metal is not a simple molecule and has no fixed molecular formula.
The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure. The sharing of delocalised electrons gives rise to strong metallic bonds. The bonding in metals may be represented in the following form:
Metal atoms have few outer-shell electrons. In a giant metallic lattice, each metal atom releases these outer electrons into a shared pool. The electrons become delocalised: they are not attached to any one atom and can move throughout the whole structure. The positive metal ions remain in fixed positions, and the attraction between these ions and the delocalised electrons produces strong metallic bonds. This model explains why metals conduct electricity and heat, and why they have high melting points. For example, in sodium, each Na atom contributes one electron to the delocalised sea, forming Na⁺ ions. In magnesium, each Mg atom contributes two electrons, forming Mg²⁺ ions, so the bonding is stronger and the melting point is higher. Diagrams show positive ions in a regular arrangement surrounded by negative delocalised electrons.
Your focus
- Describe the giant regular structure of a metal.
- Explain the role of delocalised electrons in metallic bonding.
- Link the structure of a metal to at least one of its physical properties.
Show all 6 objectives
- Describe the arrangement of positive metal ions and delocalised electrons in a giant metallic structure.
- Explain how the sharing of delocalised electrons gives rise to strong metallic bonds.
- Relate the mobility of delocalised electrons to the electrical and thermal conductivity of metals.
Metallic bonding exam tips
Marking Points
- State that metals form giant structures containing very large numbers of atoms.
- Describe the atoms as arranged in a regular, repeating pattern or lattice.
- Explain that the outer electrons become delocalised and are shared throughout the structure.
- Relate the regular lattice and delocalised electrons to properties such as conduction or malleability.
- Recognise that the structure is not molecular, so a simple molecular formula does not apply.
- Outer-shell electrons of metal atoms become delocalised, meaning they are not associated with any particular atom and are free to move through the entire metallic structure.
- The structure consists of positive metal ions arranged in a regular giant lattice, with delocalised electrons occupying the spaces between them.
- Metallic bonding arises from the strong electrostatic attraction between the positive metal ions and the shared delocalised electrons.
- The number of delocalised electrons per atom affects bond strength: magnesium contributes two electrons per atom, giving stronger metallic bonding and a higher melting point than sodium, which contributes one.
- Delocalised electrons can carry charge and kinetic energy through the metal, explaining why metals are good conductors of electricity and heat.
Examiner Tips
- 💡Use the terms giant structure, regular pattern or lattice and delocalised electrons in your answer.
- 💡Link the structure to a named property, such as electrical conductivity, to gain credit for explanation.
- 💡Sketch a simple two-dimensional lattice with plus signs for ions and dots for electrons if a diagram is requested.
- 💡When drawing a metal lattice, show positive ions in a regular pattern and label the delocalised electrons clearly; include the charge on the ions, such as Na⁺ or Mg²⁺.
- 💡Use the phrase 'delocalised electrons' rather than 'free electrons' to match the specification wording.
- 💡Link the number of outer electrons per atom to the strength of metallic bonding when comparing metals such as sodium and magnesium.
Common Mistakes
- Describing a metal as a molecule or as simple molecules; correct by stating it is a giant lattice of atoms or ions.
- Saying the atoms are randomly arranged; correct by stating the arrangement is regular and repeating.
- Claiming the delocalised electrons are attached to one particular atom; correct by explaining they are shared throughout the structure.
- Thinking that metal atoms share pairs of electrons in a covalent bond. Correction: in metallic bonding, outer electrons are delocalised and shared across the whole structure, not localised between two atoms.
- Believing that the positive ions are free to move in a solid metal. Correction: the positive ions are fixed in a regular lattice; only the delocalised electrons move.
- Stating that metallic bonds are weak because electrons are free. Correction: the attraction between the positive ions and the delocalised electrons is strong, which is why metals have high melting points.