3.1.3.1 Ionic bonding

• Ions are charged particles that can be positively or negatively charged.
• How do ions form?

  Ions are formed when electrons are transferred from one atom to another.
• Ionic equation of Na:


  Na ---> Na+ + e–.
• Ionic equation of Cl

  Cl + e–  --> Cl–.
• Ionic equation of Mg

  Mg -->  Mg2+ + 2e–.
• Ionic equation of O

  O + 2e– --> O2–.
• What are positive ions called?


  Cations
• What are negative ions called?


  Anions
• What is an ionic compound?


  Electrostatic attraction between positive and negative ions together forms a lattice. It is very strong. When oppositely charged ions come together and form ionic bonds you get an ionic compound.
• What is ionic bonding?


  Electrostatic attraction between oppositely charged ions in a lattice.
• Compound ions

  Sulfate SO42-

  Hydroxide OH-

  Nitrate NO3-

  Carbonate CO32-

  Ammonium NH4+
• What is a giant ionic lattice?


  A regular structure made of repeated ions
• Explain why ionic compounds conduct electricity when molten or dissolved? 


  The ions are free to move in a liquid and carry a charge
• Explain why solid ionic compounds don’t conduct electricty.

  Ions in a fixed position by strong ionic bonds
• Why do ionic compounds have a high melting point?


  String electrostatic forces of attraction between oppositely charged ions which takes a lot of energy to overcome
• Why can ionic compounds dissolve in water?


  Solubility. Water molecules are polar oxygen has a small negative charge, and hydrogen has a slightly positive charge. The water molecules pull the ions away from the lattice and cause it to dissolve.
• What happens to ions as you go down a group?

  Ionic radius increases
• What happens if the charge of an ion is greater? 


  The stronger the ionic bond
• What happens as the ion gets smaller? 


  The stronger the ionic bonds
• When are the melting point of ionic bonds higher?

  When the ion is smaller and has a stronger charge
• Explain, in terms of structure and bonding, why magnesium chloride has a high melting point.

  ionic lattice / lots of Mg2+ and Cl– ions Strong (electrostatic) forces of attraction

  Between Mg2+ and Cl– ions
• Suggest why the melting point of sodium iodide is lower than the melting point of sodium bromide.

  Iodide ion is bigger , so less attraction to the Na+ ion
• The melting point of sodium chloride is much higher than that of sodium metal. What can be deduced from this information?


  ionic bonding in NaCl is stronger/requires more energy to break than the metallic bonding in Na
• Compare the electrical conductivity of solid sodium metal with that of solid sodium chloride. Explain your answer.

  Sodium conducts and sodium chloride does NOT conduct

  due to delocalised electrons

  Ions can’t move in solid salt
• Which statement about inorganic ionic compounds is always correct?

  They form giant structures.