AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Deduce that a compound is ionic from a diagram of its structure in one of…
Full specification wording
Ionic compounds: deduce that a compound is ionic from a diagram of its structure in one of the specified forms
An ionic compound diagram shows a giant lattice: a regular, repeating grid of ions held in fixed positions.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 3 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
An ionic compound diagram shows a giant lattice: a regular, repeating grid of ions held in fixed positions. To deduce that a compound is ionic, look for charged particles rather than neutral atoms or molecules. In dot and cross diagrams, each ion carries a charge label such as Na⁺ or O²⁻, and electrons are shown transferred from metal to non-metal, giving full outer shells. In ball and stick or space-filling models, the pattern repeats in three dimensions with each ion surrounded by oppositely charged neighbours, for example six around each ion in sodium chloride. The key clue is a giant regular arrangement of ions, not separate molecules. If the diagram shows shared pairs of electrons between neutral atoms, it represents a covalent substance instead.
What earns the marks
- Identify that the diagram shows ions, indicated by charge labels such as Na⁺, Mg²⁺, Cl⁻ or O²⁻, rather than neutral atoms.
- Recognise a giant regular lattice that repeats in three dimensions, with each ion surrounded by oppositely charged ions.
- Link the transfer of electrons from a metal to a non-metal to the formation of full outer shells and charged ions.
- Distinguish ionic diagrams from covalent diagrams, where atoms share electron pairs and no ions are present.
- Use the ratio of ions in the diagram to support the deduction, for example one Mg²⁺ for every two Cl⁻ in magnesium chloride.
Common mistakes and how to put them right
Treating a dot and cross diagram of ions as showing shared electrons.
Put it right: In an ionic diagram the electrons are transferred, so each ion has a full outer shell and a charge label.
Assuming any regular pattern means ionic.
Put it right: Check for charged particles, because some covalent substances also form regular giant structures.
Reading a ball and stick model as separate molecules.
Put it right: The sticks show attractions between ions in a continuous lattice, not covalent bonds between molecules.
Exam tips
- Scan the diagram first for charge labels or square brackets around ion symbols, as these are the quickest evidence of ionic bonding.
- State the deduction and then justify it with one feature of the diagram, such as the repeating lattice or the transferred electrons.
- If the diagram shows neutral atoms sharing pairs, say so explicitly and explain that this indicates covalent bonding instead.
Try the lesson
The start of the Ionic compounds: deduce that a compound is ionic from a diagram of its structure in one of the specified forms lesson, made from checked teaching notes for this specification point.
Have a go first
The diagram represents part of a solid structure.
[Na⁺] [Cl⁻] [Na⁺] [Cl⁻] [Na⁺] [Cl⁻] [Na⁺] [Cl⁻] [Na⁺]
What can the student deduce about the compound?
Listen
An ionic compound diagram shows a giant lattice: a regular, repeating grid of ions held in fixed positions. To deduce that a compound is ionic, look for charged particles rather than neutral atoms or molecules. In dot and cross diagrams, each ion carries a charge label such as Na⁺ or O²⁻, and electrons are shown transferred from metal to non-metal, giving full outer shells. In ball and stick or space-filling models, the pattern repeats in three dimensions with each ion surrounded by oppositely charged neighbours, for example six around each ion in sodium chloride. The key clue is a giant regular arrangement of ions, not separate molecules. If the diagram shows shared pairs of electrons between neutral atoms, it represents a covalent substance instead. A strong answer earns marks for these points. Identify that the diagram shows ions, indicated by charge labels such as Na⁺, Mg²⁺, Cl⁻ or O²⁻, rather than neutral atoms. Recognise a giant regular lattice that repeats in three dimensions, with each ion surrounded by oppositely charged ions. Link the transfer of electrons from a metal to a non-metal to the formation of full outer shells and charged ions. Distinguish ionic diagrams from covalent diagrams, where atoms share electron pairs and no ions are present. A common slip: Treating a dot and cross diagram of ions as showing shared electrons. Instead, in an ionic diagram the electrons are transferred, so each ion has a full outer shell and a charge label. Exam tip: Scan the diagram first for charge labels or square brackets around ion symbols, as these are the quickest evidence of ionic bonding.
See it
Key words
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Ionic bonding
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Giant ionic lattices
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Electron transfer
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Representing structures
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See every definition
- Ionic bonding
- Bonding shown when electrons are transferred from a metal to a non-metal, giving charged ions with full outer shells.
- Giant ionic lattices
- A regular, repeating grid of ions held in fixed positions, repeating in three dimensions with each ion surrounded by oppositely charged neighbours.
- Electron transfer
- Electrons shown transferred from metal to non-metal, giving full outer shells and charged ions rather than shared pairs.
- Representing structures
- Diagrams such as dot and cross, ball and stick or space-filling models, where charged particles rather than neutral atoms or molecules show an ionic compound.
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