Ionic CompoundsOxford AQA IGCSE Chemistry: Revision notes
Section 1
What is an ionic compound?
An ionic compound is a giant structure of ions held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions throughout the structure, not just between one pair of ions — this is what is meant by ionic bonding.
Section 2
The structure of sodium chloride
You should be familiar with the structure of sodium chloride (NaCl) as the standard example of an ionic compound:
- Sodium ions (Na⁺) and chloride ions (Cl⁻) alternate in a regular, repeating 3D pattern
- Each Na⁺ ion is surrounded by Cl⁻ ions, and each Cl⁻ ion is surrounded by Na⁺ ions
- The strong electrostatic attraction between the oppositely charged ions in every direction holds the giant lattice together
In the sodium chloride lattice, each ion is surrounded by six ions of the opposite charge, giving a very stable, tightly packed structure.
Section 3
Why is the structure called 'giant'?
The word 'giant' shows that this pattern of alternating ions is not limited to a small group — it repeats over and over in all three directions to build up a large crystal. There is no single 'molecule' of an ionic compound; instead, the whole crystal is one continuous structure of ions.
Do not describe NaCl as 'molecules of NaCl' — ionic compounds do not exist as individual molecules, only as a continuous giant lattice of ions.
Must Know
- An ionic compound is a giant structure of ions
- Ions are held together by strong electrostatic forces of attraction between oppositely charged ions
- These forces act in all directions, not just between one pair of ions
- Sodium chloride (NaCl) is the standard example: Na⁺ and Cl⁻ ions alternate in a regular 3D lattice
- There is no such thing as a single 'molecule' of an ionic compound
That's the notes covered.
Carry on to the next subtopic.