Specification Point 1.41:
Understand ionic bonding in terms of electrostatic attractions

Ionic Bonding

Ionic Bonding: Bond between metal and non-metal with strong electrostatic forces of attraction between oppositely charged ions.

Example of an ionic bond:

Ionic bonding in NaCl, CIE IGCSE Chemistry

Ionic Bonding in Sodium Chloride ( NaCl )

Specification Point 1.42:
Understand why compounds with giant ionic lattices have high melting and boiling points

Giant Ionic Lattices

Giant Ionic Lattice: Giant three-dimensional lattice structure held together by the strong attraction between oppositely charged ions.

Example:

Lattice structure of NaCl, Edexcel IGCSE Chemistry

The lattice structure of Sodium Chloride

Crystal lattice of NaCl. Edexcel IGCSE Chemistry

Positions of the ions in a crystal of Sodium Chloride

Melting and boiling point of compounds with giant ionic lattices:

  • Melting and boiling point depends on the force that holds the particles.
  • Giant Ionic Lattices are held together by the strong attraction between oppositely charged ions with many ions and bonds in structure.
  • Large amounts of heat energy is needed to overcome forces and break down the bonds.
  • Therefore compounds with giant ionic lattices have high melting and boiling points.
  • Ionic charge is directly proportional to the melting and boiling point in an ionic compound.

e.g. Magnesium oxide has higher melting point that NaCl. This is because in MgO, 2+ ions are attracting 2- ions and in sodium chloride, the attraction is weaker because there are only 1+ and 1- ions attracted.

Specification Point 1.43:
Know that ionic compounds do not conduct electricity when solid, but do conduct electricity when molten and in aqueous solution

Ionic Compounds & Electrical Conductivity

Ionic Compounds: Formed when atoms of metals transfer electrons to atoms of non-metals to form compounds made up of ions.

Electrical conductivity of ionic compounds, Edexcel IGCSE Chemistry

Particles of ionic compounds in solids and when molten or in solution form

Electrical Conductivity of Ionic Compounds:

  • Ionic compounds cannot conduct electricity when solid as ions are fixed in structure and are not free to move.
  • However, ionic compounds can conduct electricity when molten or in aqueous solution as their ions are free to move to conduct an electric charge.

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.