5.0 Characteristics of Covalent Compounds

  Chemical Bonding and Molecular Structure

Melting Point and Boiling Point:

In covalent compounds, except those consisting of giant molecules, the molecules are less powerfully attracted to each other, as a result of which their melting points and boiling points are relatively low compared to ionic compounds, e.g.,

Conductivity:

Covalent substances (whether of the “molecular lattice” or “giant molecule” type) do not conduct electricity in the fused state since there are no free electrons or ions to carry the current. However, substances like graphite which consists of separate layers conduct electricity because the electrons have a passage in between the two flat layers.

Solubility: The characteristic solubility of covalent compounds in non-polar solvents such as benzene and carbon tetrachloride can be described to the similar covalent nature of the molecules of solute and solvent (i.e., like dissolves like). Covalent compounds in solution react more slowly as compared with the ionic compounds which react instantaneously in solution.

The solubility of covalent compounds is, however, very much dependent upon the size of the molecule.

Thus, covalent substances having giant molecules are insoluble in virtually all solvents due to the big size of the molecule unit.