Ionic Compounds: Bonds, Structure & Properties

Specification Point 1.41:

Understand ionic bonding in terms of electrostatic attractions

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 Sodium Chloride ( NaCl )

Specification Point 1.42:

Understand why compounds with giant ionic lattices have high melting and boiling points

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

Example:

The lattice structure of Sodium Chloride

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

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.