Physical Properties of Ionic and Covalent Compound

Melting Point

Ionic compounding are typically solid and usually have high melting and boiling points. In contrast covalent compound are typically gases, liquids or low melting solids. These differences occur because of differences in bonding and structure. Ionic compounds are made up of positive and negative ions arranged in a regular way in a lattice. The attraction between ions is electrostatic and is non-directional, extending equally in all direction. Melting of the compound involves breaking of the lattice. This requires considerable energy and hence melting and boiling points are usually high and the compounds are very hard. Compounds with covalent bonds are usually made up of discrete molecule. The bonds are directional and strong covalent bonding forces hold the atom together to make a molecule. In the solid molecules are held together by weak Vander Waals forces. To melt or boil the compound we simply have to supply amount of energy to break Vander Waal forces. Hence compounds are often gases, liquid or soft solids with low melting points.

§  Melting- Change from solid to liquid

§  Melting Point- Specefic tempreture whem melting occurs

§  Each pure substance has a specific melting point.

Example;

               Melting point for water-0^oC (32^oF)

               Melting point for Nitrogen- (-209.9^oc)

               Melting point for Silver- 961^.93 ^oC

              Melting point for Corban- 3500.0^oC

Conductivity

Ionic compounds conduct electricity when the compound is melted or in aqueous solution. Conduction is achieved by the ions migrating towards the electrodes under the influence of electric potentials. Covalent compounds contain neither ions nor mobile electrons so they are unable to conduct electricity in either solid or gaseous state.

Solubility

Ionic compounds are usually soluble in polar solvents. There are solvents if high dielectric constant such as water or mineral acids. Covalent compounds are not normally soluble in polar solvents but they are soluble in non-polar solvents of low dielectric constant such as benzene or CCl₄.