Properties of Covalent Substances

Ellen Oakley

What are covalent bonds?

A covalent bond is where non-metal atoms, each bond consisting of a shared pair of electrons, making them strong bonds. Covalent substances fall into two main groups:

Simple molecular covalent substances & Giant molecular covalent substances.

Simple Molecular Covalent Substances

Simple covalent substances, such as hydrogen gas and water, have low melting and boiling points as even though the bond between the individual atoms, there is a week intermolecular force/attraction between the molecules and so the energy, in the form of thermal energy, required to break apart the weak intermolecular bonds is little, meaning they have low boiling and melting points.

Simple covalent substances are also non conductive or poor conductors because they have no free electrons, no charged particles at all able to move around or an overall electric charge.

Giant Molecular Covalent Substances

Giant covalent substances, such as graphite and diamond, have high melting and boiling points as they have strong intermolecular forces and strong covalent bonds between the, typically, carbon atoms. However certain substances have different properties:

Diamond - it's very hard because all the atoms are joined with strong covalent bonds. Diamonds make good cutting tools. It also doesn't conduct electricity because there are no free electrons or charged particles to move around/flow.

Graphite - easily rubs away in layers because although the covalent bonds within the layers are very strong, there are only weak forces between the layers. It is soft enough to be used as a lubricant. I t can also conduct electricity because there is one electron from each carbon atom that can move along the layers. This means that graphite can be used to make electrodes.