Ionic Compounds — Properties and Structure

This lesson covers the structure of ionic compounds and how it explains their physical properties, as required by AQA GCSE Combined Science Trilogy (8464), section 4.2.1. You need to understand the giant ionic lattice, explain why ionic compounds have high melting points, and know when they conduct electricity.

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The Giant Ionic Lattice

Ionic compounds do not exist as individual pairs of ions. Instead, the ions are arranged in a regular, repeating three-dimensional pattern called a giant ionic lattice. In this lattice:

• Each positive ion is surrounded by negative ions, and vice versa.
• The electrostatic forces of attraction act in all directions — every ion attracts all nearby ions of opposite charge.
• There are no individual molecules — the formula (e.g. NaCl) gives the simplest ratio of ions.

graph TD
    A["Giant Ionic Lattice"] --> B["Regular repeating<br/>3D arrangement"]
    A --> C["Strong electrostatic<br/>forces in ALL directions"]
    A --> D["No individual<br/>molecules"]
    B --> E["Each ion surrounded<br/>by oppositely charged ions"]
    C --> F["High melting and<br/>boiling points"]

    style A fill:#2c3e50,color:#fff
    style B fill:#2980b9,color:#fff
    style C fill:#2980b9,color:#fff
    style D fill:#2980b9,color:#fff
    style E fill:#27ae60,color:#fff
    style F fill:#27ae60,color:#fff

Sodium Chloride Lattice