5.7.1 Physical Properties – Ionic Compounds

Structure Ionic Compound

1. In an ionic compound, the alternate positive and negative ions in an ionic solid are arranged in an orderly way as shown in the image to the right.
2. The ions can form a giant ionic lattice structure with ionic bond between the ions.
3. The ionic bond is the strong electrical attraction (electrostatic force) between the positive and negative ions next to each other in the lattice.

(Giant Lattice Structure)

(Strong Electrostatic Force formed between the positive and negative ions)

Properties of Ionic Compounds

1. The strong bonding force makes ionic compounds has high melting and boiling points.
2. All ionic compounds are crystalline solids at room temperature.
3. They are hard but brittle, when stressed the bonds are broken along planes of ions which shear away.
4. Many, ionic compounds (but not all) are soluble in water.
5. The solid crystals DO NOT conduct electricity because the ions are not free to move to carry an electric current.
6. However, if the ionic compound is melted or dissolved in water, the liquid will now conduct electricity, as the ion particles are now free.