2.1.5Bonds, Structure and Properties of Matter

Metallic Bonding — AQA GCSE Combined Science Trilogy 8464 - Chemistry Revision Notes & Topical Questions

10 min read 12 parts Lesson 6 of 18

📚 AQA GCSE Combined Science Trilogy 8464 - Chemistry Hub / Topical Revision

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Part 1 of 12Key ideas

Key ideas

Metals are giant lattices of positive ions in a sea of delocalised electrons — there are no separate metal molecules.

Electrons only

The current in a solid metal is carried by electrons only; the positive ions stay in the lattice.

Malleability and ductility are possible because sliding layers remain attracted to the delocalised electrons.

Most metals have high melting points because the electrostatic attraction is strong — but melting points vary between metals.

Metals conduct heat as well as electricity

Metals conduct heat as well as electricity mobile electrons plus a closely packed lattice transfer energy.

Deduct a metal's structure from data

Deduct a metal's structure from data conducts when solid and molten → giant metallic.

Alloys are harder than the pure metal because differently sized atoms stop the layers sliding as easily.

Do not use the word "free" for electrons in an exam answer — write "delocalised".

Part 2 of 12The metallic structure

A metal is a giant lattice of positive ions surrounded by delocalised electrons.

Outer-shell electrons are no longer associated with only one atom and can move through the structure.

The bonding is the strong electrostatic attraction between those positive ions and the delocalised electrons.

A labelled diagram must show both the ion lattice and the electrons, and must not show separate metal molecules.

Part 3 of 12Why metals conduct

Why metals conduct

The delocalised electrons are mobile; when a potential difference is applied their overall movement transfers charge.

The positive ions do not flow through the solid.

Thermal energy is also transferred efficiently, by mobile electrons and by vibrations of the closely packed lattice.

Part 4 of 12Why metals can be shaped

Why metals can be shaped

When a force is applied, layers of positive ions slide past one another while remaining attracted to the delocalised electrons.

So a metal can be hammered into sheets or drawn into wires instead of shattering.

Contrast with an ionic crystal

Contrast with an ionic crystal sliding can bring like charges beside one another, causing repulsion and fracture.

Part 5 of 12Melting point

Melting point

Substantial energy is needed to overcome the strong electrostatic attractions, so most metals melt at high temperature.

Melting points are not all high — they vary between metals, so avoid absolute claims.

Part 6 of 12Alloys

An alloy is a mixture containing a metal and one or more other elements; some alloys contain a non-metal.

Different-sized atoms disrupt the regular arrangement, so the layers cannot slide as easily and the alloy is harder.

Brass = copper + zinc (instruments, door knobs). Stainless steel = iron + chromium + nickel + carbon (cutlery, rust resistant). Aluminium alloy = Al + Cu + Mn + Si (aircraft: strong, low density).

Do not claim that every alloy has every property improved — the explanation is about disrupted layers.

Part 7 of 12Use-linked properties (0620 metals board)

Copper

Copper electrical wiring (very good conductor, ductile); water pipes (non-toxic, unreactive with water, malleable); saucepan bases (conducts heat, unreactive).

Aluminium

Aluminium aircraft bodies (high strength-to-weight, low density); overhead cables (good conductor, low density); food cans (non-toxic, corrosion- and acid-resistant).

Aluminium appears unreactive because it carries a protective aluminium oxide layer.

Part 8 of 12Process & sequence

- Metal atom has 1, 2 or 3 outer-shell electrons
- Those outer electrons become delocalised — spread through the whole structure
- Positive ions are left and pack into a regular lattice
- Strong electrostatic attraction acts between every ion and the surrounding electrons
- Attraction holds the lattice together in all directions
- Mobile electrons carry charge → electrical conduction; energy moves through the lattice → thermal conduction
- Layers slide under force, attraction is maintained → malleable, ductile
Build the explanation of malleability in this order; each step is a marking point.
1. Metal atoms lose outer-shell electrons, which become delocalised.
2. Positive ions form and are packed in regular layers.
3. Electrostatic attraction acts between the ions and the surrounding electrons.
4. A force is applied to the metal.
5. The layers of positive ions slide over one another.
6. The attraction between ions and delocalised electrons is maintained, so the structure does not shatter.

Part 9 of 12Worked examples

Worked examples

Deducing a structure from physical data

Substance D
- melting point 1500 °C, conducts when molten only, does not conduct as a solid → giant ionic lattice;
  - the ions are fixed in the solid and only mobile when molten.
Substance E
- melting point 2500 °C, never conducts → giant covalent structure;
  - all outer electrons are held in bonds.
Substance that conducts as a solid and when molten, with a high melting point → giant metallic lattice: the delocalised electrons are mobile in both states.
Low melting point, no conduction in any state → simple molecular: weak intermolecular forces, uncharged molecules.

Writing a two-mark definition of metallic bonding

Award the marks for: electrostatic attraction + between positive ions and delocalised electrons.
Describing only "a lattice of atoms" scores nothing — the particles and the type of attraction must both be named.

Explaining why an alloy is harder (3 marks)

Mark 1: the alloy contains atoms of different sizes.
Mark 2: this distorts / disrupts the regular arrangement of layers.
Mark 3: so the layers cannot slide as easily over one another.

Part 10 of 12Summary

- Metallic bonding is the electrostatic attraction between positive ions and delocalised electrons.
- Conduction of electricity is due to mobile electrons, never to moving ions.
- Metals are malleable and ductile because layers of ions slide while attraction continues.
- High melting points come from strong electrostatic attraction, which needs much energy to overcome.
- Alloys are mixtures that are harder because different-sized atoms distort the layers.

Part 11 of 12Keep going

Metallic bonding IGCSE Chemistry 0620: what to do next
These Metallic bonding IGCSE Chemistry 0620 notes covered the key ideas, worked examples and exam technique for this topic. Check your Metallic bonding IGCSE Chemistry 0620 understanding with the practice questions below, then reread any Metallic bonding IGCSE Chemistry 0620 point you were unsure about before moving on.
Metallic bonding IGCSE Chemistry 0620: revision checklist
- Revise the main Metallic bonding IGCSE Chemistry 0620 definitions until you can write them from memory.
- Practise Metallic bonding IGCSE Chemistry 0620 exam questions under timed conditions.
- Link each Metallic bonding IGCSE Chemistry 0620 idea to a diagram or a worked example.
- Practice: Metallic bonding IGCSE Chemistry 0620 practice questions
- Previous lesson: 2.6 Giant Structures — 0620 Notes
- Next lesson: 4.1 Electrolysis — 0620 Notes
- Course: Cambridge IGCSE Chemistry 0620 — all units
- Official syllabus: Cambridge IGCSE Chemistry 0620 syllabus

Part 12 of 12Compare: Compare

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Three giant or simple structures compared
Feature	Giant ionic	Giant metallic	Simple molecular
Particles	Positive and negative ions	Positive ions + delocalised electrons	Discrete molecules
Attraction	Electrostatic, oppositely charged ions	Electrostatic, ions to delocalised electrons	Weak intermolecular forces
Melting / boiling point	High	Usually high (varies between metals)	Low
Conducts when solid	No — ions fixed	Yes — electrons move	No — uncharged molecules
Conducts when molten	Yes — ions move	Yes	No
Shape change	Not malleable; layers repel when they slide	Malleable and ductile	Soft or brittle

Pure metal compared with its alloy
Feature	Pure metal	Alloy
Atom sizes	Regular layers of similarly sized atoms	Different-sized atoms distort the regular arrangement
Layers under force	Can slide relatively easily	Sliding of layers is hindered
Result	Often softer	Often harder and stronger
Example from the boards	Iron	Brass (copper + zinc); stainless steel (iron + Cr + Ni + C)
Is it a compound?	—	No — an alloy is a mixture, not chemically combined

Key terms

Exam technique

Words that lose marks

Delocalised

"Free electrons" — write delocalised instead; "free" is not accepted for electrons or ions.

Electrons only

"Moving atoms" or "moving ions" carry the current in a metal — the charge carriers are electrons only.

Intermolecular forces

"Weak covalent bonds" when a low melting point is being explained — covalent bonds are strong; the intermolecular forces are weak.

Definition questions

Name both particle types and the type of attraction; a diagram is not a definition.

For "explain the property", the answer must link structure → property; a bare fact scores nothing.

Data questions

Use conduction in the solid state as the discriminator: only metallic structures conduct as solids.

Check melting point as well as conductivity before naming a giant structure.

Alloys

Alloys answer mixture, never compound, unless the question states the elements are chemically combined.

Diagrams

Show alternating positive ions in contact, with electrons spread between them; label both the ions and the delocalised electrons.

Do not draw pairs of atoms as molecules.

Last updated: 20 October 2026