Properties of Ionic Compounds (CIE IGCSE Chemistry: Co-ordinated Sciences (Double Award))

• 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

Extended tier only

• Ionic compounds have high melting and boiling points
  • They have giant structures
  • There are strong electrostatic forces of attraction between oppositely charged ions in all directions
  • The forces need lots of energy to overcome them 
• Ionic compounds are poor conductors in the solid state
  • The ions are in fixed positions in the lattice
  • They are therefore unable to move and carry a charge 
• Ionic compounds are good conductors of electricity in the molten state or in solution 
  • When the ionic compound is melted or dissolved in water, the ions are able to move and carry a charge

• 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^-

Diagram to show the electrical conductivity of ionic compounds

Molten or aqueous ions move freely but cannot in solid form