Properties of Ionic Compounds

Overview

Ionic compounds are composed of charged particles known as ions.
They have a giant lattice structure with strong electrostatic forces of attraction between oppositely charged ions.

Ionic compounds have regular structures called giant ionic lattices.
The electrostatic forces act in all directions between the oppositely charged ions.
This structure accounts for many of the physical and chemical properties of ionic compounds.

Key Fact: Ionic compounds have high melting and boiling points and are solid at room temperature.
Energy must be added to overcome the strong electrostatic forces during melting and boiling:
- Some forces are overcome during melting.
- All remaining forces are overcome during boiling.
The stronger the forces (due to higher charge on ions), the higher the melting and boiling points.
Examples:
- NaCl has a melting point of 801°C and boiling point of 1,413°C.
- MgO has a melting point of 2,852°C and boiling point of 3,600°C.

Ionic compounds conduct electricity when melted or dissolved in water:
- Melting or dissolving allows ions to move freely.
- In the solid state, ions are fixed in place and cannot move, so they do not conduct electricity.
Key Fact: Ionic compounds are insulators when solid but conductors when melted or in aqueous solution.

Learn more about properties in related topics such as the three states of matter and changes of state.

For further details, refer to the full guide on BBC Bitesize.