Free Science Lessons: Ionic Compounds

Introduction

• Objective:
  • Describe formation of giant ionic lattices in ionic compounds.
  • Explain high melting and boiling points of ionic compounds.
  • Explain electrical conductivity of ionic compounds when solid, molten, or dissolved.

Ionic Bonding Recap

• Occurs Between:
  • Metals and non-metals.
• Example:
  • Reaction of sodium (Na) with chlorine (Cl) leads to transfer of one electron from Na to Cl.
  • Formation of sodium ion ((Na^+)) and chloride ion ((Cl^-)).
  • Both ions achieve stable electronic structure, similar to noble gases.

Sodium Chloride (NaCl) as an Ionic Compound

• Formation of Crystals:
  • NaCl forms a crystal structure.
• Ions Arrangement:
  • Giant ionic lattice structure.
  • Positive ions surrounded by negative ions and vice versa.
• Nature of Lattice:
  • Three-dimensional.

Electrostatic Forces in Ionic Lattices

• Characteristics:
  • Strong forces of attraction between (Na^+) and (Cl^-) ions.
  • Called electrostatic forces of attraction or ionic bonds.
  • These forces act in all directions.

Properties of Ionic Compounds

High Melting and Boiling Points

• Reason:
  • Strong electrostatic forces require significant heat energy to break.
• Example:
  • Sodium chloride has a melting point around 800°C.

Electrical Conductivity

• Solid State:
  • Ionic compounds do not conduct electricity; ions are locked in place.
  • Only able to vibrate, not move.
• Molten or Dissolved State:
  • Ions can move freely, enabling conduction of electricity.
  • Important to note: It's the ions, not electrons, that move and carry charge.

Conclusion

• Exam Tip:
  • Remember that movement of ions, not electrons, is responsible for electrical conduction in ionic compounds.
• Additional Resources:
  • For further practice, refer to the revision workbook linked in the lesson.