Properties of Ionic Compounds (AQA GCSE Chemistry: Combined Science)
Revision Note
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Physical Properties of Ionic Compounds
- Ionic compounds are made of charged particles called ions which form a giant lattice structure
- 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 O2- so will have a higher melting point than sodium chloride which contains the ions, Na+ and Cl-
Strong electrostatic forces act in all directions in an ionic solid such as sodium chloride
- Ionic compounds are usually solid at room temperature and are non-volatile
- They are usually water soluble as both ionic compounds and water are polar substances
Ionic compounds are soluble in water because the ions are easily hydrated by polar water molecules
Exam Tip
Ions with higher charge have stronger electrostatic forces and will thus have higher melting and boiling points.
Electrical Conductivity: Ionic Compounds
- For electrical current to flow there must be freely moving charged particles such as electrons or ions present
- Ionic compounds can conduct electricity in the molten state or in solution as they have ions that can move and carry charge
- They cannot conduct electricity in the solid state as the ions are in fixed positions within the lattice and are unable to move
Molten or aqueous particles move and conduct electricity but cannot in solid form
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