Metallic bonding, conduction and shaping
Explain metallic properties with positive ions and mobile delocalised electrons.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recognise electrostatic attraction between opposite charges.
- Explain why conductivity requires mobile charge carriers.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which charge combination gives electrostatic attraction?
What you will learn
- Describe metallic bonding as electrostatic attraction.
- Explain electrical conductivity, malleability and ductility using the metallic model.
Positive ions and delocalised electrons
In the metallic model, positive metal ions form a giant arrangement surrounded by delocalised outer electrons. The electrons are not restricted to one bond between two atoms. Strong electrostatic attraction between the positive ions and these electrons holds the metal together; this attraction is metallic bonding.
When a potential difference is applied, delocalised electrons move through the metal and carry current. The positive ions mainly vibrate about their positions in a solid; they do not flow through the wire as the current carriers. A metal also conducts when molten because its mobile electrons remain available.
Bonding can remain as the layers shift
Malleability means a material can be hammered or pressed into shapes; ductility means it can be drawn into wires. In a metal, layers of positive ions can shift while remaining attracted to the surrounding delocalised electrons. Bonding therefore persists through deformation instead of requiring one rigid set of directional atom-to-atom links to remain aligned.
This does not mean a metal has no bonds or that all metals are equally easy to shape. The simple model explains the characteristic behaviour of many metals. A detailed comparison of alloys, hardness and the properties of particular metals belongs to later topics.
Sources for this lesson
Pause and explain
What carries current in a solid copper wire?
Worked example
Explain why copper conducts electricity and can be drawn into wire.
Show the worked solution
- Copper contains delocalised electrons that can move and carry charge.
- Its positive ions remain attracted to those electrons.
- Ion layers can shift during shaping while metallic attraction persists.
Answer Mobile electrons allow conduction; persistent attraction during layer movement allows ductility.
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Test this topic →From guided practice to a new situation
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.
Describe the particles and attraction in a giant metallic structure.
Give me a hint
State both charges and the location of the mobile electrons.
Compare my reasoning
- Positive metal ions form an extended arrangement.
- Delocalised electrons can move through that arrangement.
- Electrostatic attraction between ions and electrons provides metallic bonding.
Positive ions attracted to mobile delocalised electrons in a giant structure.
Look for these in your work
- Both components are named.
- Attraction is distinguished from electron movement under voltage.
Explain the difference between malleability and ductility, then use one particle explanation for both.
Give me a hint
Link each term to a shaping process.
Compare my reasoning
- Malleability is shaping by hammering or pressing; ductility is drawing into wire.
- Layers of positive ions can shift during deformation.
- Attraction to the delocalised electrons persists, holding the material together.
Malleable: pressed into shapes. Ductile: drawn into wires. Layer movement can occur while metallic bonding persists.
Look for these in your work
- The two terms are correctly distinguished.
- The model explains continued bonding during deformation.
A metal and an ionic compound both conduct when molten. Why does this not show that they have the same charge carriers or bonding?
Give me a hint
Compare mobile electrons with mobile ions.
Compare my reasoning
- The molten metal conducts through delocalised electrons.
- The molten ionic compound conducts through moving positive and negative ions.
- Metallic attraction is between ions and electrons; ionic attraction is between opposite ions.
Similar molten conductivity can arise from different charge carriers and bonding models.
Look for these in your work
- The carrier in each melt is correct.
- The two attractions are clearly distinguished.
Common mistakes
- Saying the positive ions travel down a solid wire to carry current.
- Describing metallic bonding as repulsion between positive ions.
What can you explain now?
Name the two components that attract in metallic bonding.
Compare with the explanation
Positive metal ions and delocalised electrons
Their opposite charges give electrostatic attraction throughout the giant metallic arrangement.
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Make it stick
Explain conduction and ductility using one labelled metallic model. Contrast its charge carriers with those in molten sodium chloride.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.