GCSE · Chemistry · AQA · Spec 8462

Metals as conductors

A metal spoon left in hot tea soon has a hot handle. Metal wires carry electricity to your lamp. Two different jobs — one tiny reason behind both.

Look inside

Inside a solid metal

View: The structure. Showing 3 layers: Electron sea, Positive metal ions, Delocalised electrons

View

Explore

Rows of positive metal ions, with delocalised electrons spread through the whole structure. Chemists often call this a "sea" of electrons.

A metal is rows of positive ions with electrons that belong to none of them. Switch views, then tap each part to see its job.

Build the explanation

One cause, two effects

Link each idea to the one it leads to. Both explanations start from the same place — see if you can build the two chains.

The metal has delocalised electrons
The electrons can move through the whole structure
The electrons carry charge through the metal
The electrons transfer energy through the metal
Good conductor of electricity
Good conductor of thermal energy

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What really moves?

Name the carrier

A solid metal bar is connected into a circuit, and charge flows through it. Later, one end is heated, and energy spreads along it.

Which idea is closest to what you think carries the charge and the energy through the bar?

Each electron stays stuck in a bond between two particular atoms, and passes the charge along.The positive metal ions move along the bar.Delocalised electrons move through the metal, carrying the charge and transferring the energy.The metal makes new electrons, and they get used up as they travel.

How sure are you?

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Each electron stays stuck in a bond between two particular atoms, and passes the charge along.

This is a common misconception

If every electron were stuck in one place, nothing could travel through the bar — so nothing could carry charge or energy from one end to the other. In a metal the electrons are delocalised: not tied to any one ion, and free to move through the whole structure.

The positive metal ions move along the bar.

This is a common misconception

A sensible guess — ions do have a charge. But in a solid metal the ions are held in place in their regular pattern. They stay where they are. The particles that travel through the metal are the delocalised electrons.

Delocalised electrons move through the metal, carrying the charge and transferring the energy.

This matches the evidence

Spot on. The same free-moving electrons do both jobs: carrying charge gives electrical conduction, and passing energy along gives thermal conduction.

The metal makes new electrons, and they get used up as they travel.

This is a common misconception

No electrons are made or used up. The delocalised electrons are in the metal all the time. When the metal conducts, they move through it — it's what they carry, charge or energy, that gets passed along.

The carrier is the delocalised electron: not the ion, not an electron stuck in one place, and not something the metal makes.

Your turn to write

Put it into words

Explain why metals are good conductors of electricity and of thermal energy. [4 marks]

Your answer

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The mark scheme

Metals contain delocalised electrons. (1 mark)
These electrons can move through the (whole) metal structure. (1 mark)
The moving electrons carry (electrical) charge through the metal. (1 mark)
The electrons transfer (thermal) energy through the metal. (1 mark)

Model answer

Metals have delocalised electrons, which are free to move through the whole structure. As they move, these electrons carry electrical charge through the metal, so metals conduct electricity well. They also transfer thermal energy through the metal, so metals are good thermal conductors.

Name the particle (delocalised electrons), say they can move, then say what they carry for EACH property. "Free electrons flow" on its own misses what they carry, and anything about ions moving earns nothing.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Metals carry electricity and heat brilliantly. Both jobs come down to one thing hiding inside the metal — and once you can see it, you can explain both.

What you need to know

A metal's structure is positive metal ions in a regular pattern, with delocalised electrons spread through it.
Delocalised electrons are not tied to any one ion, so they are free to move through the whole metal.
Metals are good conductors of electricity because the delocalised electrons carry electrical charge through the metal.
Metals are good conductors of thermal energy because energy is transferred through the metal by the delocalised electrons.

The big picture

A metal is made of positive metal ions held in a regular pattern, with delocalised electrons that are not tied to any one ion and can move through the whole structure. Those moving electrons carry electrical charge through the metal, which is why metals are good conductors of electricity. They also transfer thermal energy through the metal, which is why metals are good thermal conductors. One feature, two properties.

Key points

1One cause, two effects: delocalised electrons explain both electrical and thermal conduction.

2Charge carried → electrical conduction. Energy transferred → thermal conduction.

3The positive ions are held in place — they are not the carriers.

4Say what the electrons DO. "Has free electrons" is not an explanation until you say they move and carry charge or energy.

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Worked example

Problem

A metal wire connects a battery to a lamp, and the lamp lights up. Explain, in terms of the metal's structure, how the wire conducts electricity.

⚠ Watch out

Saying the metal ions move to carry the current. In a solid metal the positive ions are held in place — the delocalised electrons are what move through the metal and carry the charge.

🧠

Memory hook

Free to roam, they carry the load: charge for current, energy for heat.

✓

Check yourself

Cover the page. Sketch a few positive ions and their delocalised electrons. Add two arrows from the electrons: what they carry for electricity, and what they transfer for thermal conduction.

Flashcards

(6)

What does "delocalised" mean for the electrons in a metal?

They are not tied to any one ion, so they are free to move through the whole metal.

Name the particles that make up an electric current in a metal.

Delocalised electrons — as they drift along, their charge drifts with them.

How is thermal energy transferred through a metal?

By the delocalised electrons, which move through the metal and pass the energy on.

Why aren't the positive ions the carriers in a solid metal?

They are held in place in a regular pattern, so they don't travel through the metal.

Which one feature of a metal's structure explains BOTH kinds of conduction?

Its delocalised electrons, which are free to move through the structure.

True or false: "Metals have delocalised electrons because they conduct."

False — it's the wrong way round. The delocalised electrons are the cause; conducting is the effect.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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One cause, two effects

Name the carrier

Put it into words

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