Properties of Ionic Compounds (Cambridge (CIE) O Level Chemistry): Revision Note

Properties of Ionic Compounds

What are the properties of ionic compounds?

• Ionic compounds are usually solid at room temperature 

• They have high melting and boiling points

• Ionic compounds are good conductors of electricity in the molten state or in solution 

• They are poor conductors in the solid state

Explaining the properties of ionic compounds

• Ionic substances have high melting and boiling points due to the presence of strong electrostatic forces acting between the oppositely charged ions

• These forces act in all directions and a lot of energy is required to overcome them

• The greater the charge on the ions, the stronger the electrostatic forces and the higher the melting point will be

  • For example, magnesium oxide consists of Mg²⁺ and O^2- so will have a higher melting point than sodium chloride which contains the ions, Na⁺ and Cl^-

• For electrical current to flow there must be freely moving charged particles such as electrons or ions present 

• Ionic compounds are good conductors of electricity in the molten state or in solution as they have ions that can move and carry a charge

• They are poor conductors in the solid state as the ions are in fixed positions within the lattice and are unable to move