Following are the typical characteristics of covalent compounds:
(i) Low melting and boiling points:
Covalent compounds consist of molecules held by weak forces. These can be easily overcome by heat. Thus, covalent compounds have low melting points and low boiling points.
(ii) Non-conducting nature:
Covalent compounds do not conduct electricity, i.e., electricity does not pass through the covalent compounds. This is because the covalent compounds do not contain ions, or free electrons. Sugar is a covalent compound, and its solution does not conduct electricity. Solutions of polar covalent compounds, e.g., HCl, conduct electricity due to the presence of ions in solutions.
Covalent compounds are usually insoluble not polar solvents like water. The covalent compounds however, dissolve in non-polar solvents, like benzene, toluene, etc.
(iv) Slow rate of reaction:
the reactions of the covalent compounds are quite slow. This is because the covalent compounds take part in reactions as molecules, and the molecular reactions are slow.
Covalent bonds are rigid and directional. Therefore, these can give different arrangements of atoms in space. So, a single molecular formula may represent a number of different compounds with different properties. This phenomenon is called isomerism.