Why the melting and boling point of covalent compounds low?

Answer 1

Covalent compounds are formed by the sharing of electrons. So, it is important to note that these compounds have a weak inter-molecular force. In other words, their bond is not strong as the force between their molecules is not very strong. So, it is easier to break the bonds between element. Melting or boiling or nay phase change in general is accomplished when the bonds holding the atoms together is broken.

Thus, as covalent compounds have a weak bond strength, they can be broken very easily and that is why they have low melting and boiling points.

Answer 2

The melting and boiling points of covalent compounds are generally low because the intermolecular forces between the molecules in covalent compounds, such as London dispersion forces, dipole-dipole interactions, and hydrogen bonding, are weaker than the intramolecular forces that hold the atoms together in the molecules. This results in covalent compounds requiring less energy to break these intermolecular forces and change from solid to liquid or liquid to gas compared to ionic or metallic compounds.