Properties of Ionic Compounds (Cambridge O Level Chemistry)

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