Properties of Ionic Compounds

This lesson explains the physical properties of ionic compounds and links them to the giant ionic lattice structure. Understanding why ionic compounds have high melting points, can conduct electricity under certain conditions and are often soluble in water is key to success in the Edexcel GCSE Chemistry (1CH0) exam.

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Recap: The Giant Ionic Lattice

Ionic compounds consist of a regular, repeating three-dimensional arrangement of positive and negative ions. This is called a giant ionic lattice. The ions are held together by strong electrostatic forces of attraction that act in all directions between oppositely charged ions.

The key properties of ionic compounds are all explained by this structure.

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High Melting and Boiling Points

Ionic compounds have high melting points and high boiling points.

Why?

• There are strong electrostatic forces between oppositely charged ions throughout the giant lattice.
• These forces act in all directions (not just between one pair of ions).
• A large amount of energy is needed to overcome these strong attractions and separate the ions.
• Therefore, high temperatures are required to melt or boil an ionic compound.