Ionic Compounds

This lesson covers the structure and properties of ionic compounds as required by the Edexcel GCSE Combined Science specification (1SC0). You need to understand the giant ionic lattice structure and be able to explain the typical properties of ionic compounds in terms of their bonding and structure.

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The Giant Ionic Lattice

Ionic compounds do not exist as individual molecules. Instead, they form a giant ionic lattice — a regular three-dimensional arrangement of alternating positive and negative ions extending in all directions.

Key Features

• Every positive ion is surrounded by negative ions, and every negative ion is surrounded by positive ions.
• The ions are held together by strong electrostatic forces of attraction (ionic bonds) acting in all directions.
• The lattice is described as giant because it contains billions of ions arranged in a repeating pattern.

graph TD
    A["Giant Ionic Lattice<br/>(e.g. NaCl)"] --> B["Regular 3D arrangement"]
    A --> C["Alternating +/− ions"]
    A --> D["Strong electrostatic<br/>attractions in all<br/>directions"]

    style A fill:#2c3e50,color:#fff
    style B fill:#2980b9,color:#fff
    style C fill:#27ae60,color:#fff
    style D fill:#e67e22,color:#fff

Sodium Chloride Lattice

In sodium chloride (NaCl):