Covalent compounds generally consist of nonmetals bonded together via electron sharing. Binary covalent compounds consist of two elements bonded together, and they are named as follows:

Prefix 1 + nonmetal 1 + prefix 2 + root of nonmetal 2 + -ide

For e.g. dihydrogen monoxide is the IUPAC name for H2O.

The nonmetal furthest to the left and bottom of the periodic table goes first. Only covalent compounds require a prefix to define the number of atoms of that element in the compound. This is called a multiplicative prefix.

Multiplicative prefixes follow a: Mono - 1, di - 2, tri - 3, tetra - 4 etc pattern. For five or more elements, the prefixes follow the names of regular polygons (penta, hexa, etc.)

When no more of that element can be added to the compound we apply the per- prefix. For example, in hydrogen peroxide, this element is oxygen.

Lewis structure of the peroxide molecule. A horizontal line bonds two oxygen atoms together. Each oxygen atom is also bonded to hydrogen at a 270-degree angle so the structure looks like deck chairs. The central oxygen atoms also have two lone pairs of electrons on them.

Figure 1: The lewis structure of hydrogen peroxide