AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Ionic compounds: An ionic compound is a giant structure of ions.
An ionic compound is not made of separate molecules.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 1 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
An ionic compound is not made of separate molecules. Instead, it forms a giant structure, also called a giant ionic lattice, in which huge numbers of positive and negative ions are packed together in a regular repeating pattern. Each ion is surrounded by ions of opposite charge. For example, in sodium chloride, each Na⁺ ion is surrounded by six Cl⁻ ions, and each Cl⁻ ion is surrounded by six Na⁺ ions. The structure extends in three dimensions, so there is no fixed number of ions in a single piece of the compound. The formula, such as NaCl, shows the simplest ratio of ions, not a molecule. This giant arrangement explains the high melting points of ionic compounds because many strong attractions must be overcome.
What earns the marks
- An ionic compound consists of a giant lattice of ions, not discrete molecules.
- The lattice contains many positive and negative ions arranged in a regular repeating pattern.
- Each ion is surrounded by ions of opposite charge, for example six of the opposite ion in sodium chloride.
- The chemical formula shows the simplest ratio of ions in the compound, not the number of ions in the structure.
- The giant structure extends in three dimensions and contains no fixed number of ions.
- The regular arrangement results from the attraction between oppositely charged ions.
Common mistakes and how to put them right
Describing an ionic compound as made of molecules.
Put it right: It is a giant lattice of ions, and the formula gives only the simplest ratio.
Thinking the formula NaCl means one Na⁺ ion and one Cl⁻ ion in the structure.
Put it right: The lattice contains many of each ion in a 1:1 ratio.
Saying the ions are shared or bonded covalently.
Put it right: Ionic bonding involves electrostatic attraction between oppositely charged ions.
Exam tips
- Use the term giant ionic lattice when describing the structure.
- State that the formula shows the simplest ratio of ions, not a molecule.
- Link the regular arrangement to the properties of ionic compounds, such as high melting point.
Try the lesson
The start of the Ionic compounds: An ionic compound is a giant structure of ions. lesson, made from checked teaching notes for this specification point.
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Which description best matches the structure of an ionic compound such as sodium chloride?
Listen
An ionic compound is not made of separate molecules. Instead, it forms a giant structure, also called a giant ionic lattice, in which huge numbers of positive and negative ions are packed together in a regular repeating pattern. Each ion is surrounded by ions of opposite charge. For example, in sodium chloride, each Na⁺ ion is surrounded by six Cl⁻ ions, and each Cl⁻ ion is surrounded by six Na⁺ ions. The structure extends in three dimensions, so there is no fixed number of ions in a single piece of the compound. The formula, such as NaCl, shows the simplest ratio of ions, not a molecule. This giant arrangement explains the high melting points of ionic compounds because many strong attractions must be overcome. A strong answer earns marks for these points. An ionic compound consists of a giant lattice of ions, not discrete molecules. The lattice contains many positive and negative ions arranged in a regular repeating pattern. Each ion is surrounded by ions of opposite charge, for example six of the opposite ion in sodium chloride. The chemical formula shows the simplest ratio of ions in the compound, not the number of ions in the structure. Exam tip: Use the term giant ionic lattice when describing the structure.
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Key words
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Giant ionic lattice structure
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Regular arrangement of ions
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Simplest ratio shown by a formula
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Relationship between structure and properties
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See every definition
- Giant ionic lattice structure
- A structure in which huge numbers of positive and negative ions are packed together in a regular repeating pattern.
- Regular arrangement of ions
- Each ion is surrounded by ions of opposite charge, and the structure extends in three dimensions.
- Simplest ratio shown by a formula
- The formula shows the simplest ratio of ions, not a molecule.
- Relationship between structure and properties
- The giant arrangement explains the high melting points because many strong attractions must be overcome.
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