The diagrams show the arrangement of the valence electrons on atoms of each of these non-metals. These electrons may be involved in bonding.
It is also shown in the table that each of these elements exists as a molecule containing two or more of the same atoms joined by a chemical bond. The chemical bonds between atoms of nonmetallic elements are referred to as covalent bonds.
Covalent bonds are electron pairs shared between two atoms.
The number of bonds that each of these atoms form in the molecules above can be deduced from the valence electron diagram for that atom as it is equal to the number of unpaired valence electrons.
Thus it is possible to predict, for the molecules above, the number of valence electrons involved in bonds and the number that are present as non-bonding electron pairs. The structure of the molecule that this predicts is helpful in understanding both the physical properties and reactivity of the bulk substance.
| Group | Group | Group | |
 (H2) |  (N2) |  (O2) |  (F2) |
 (P4) |  (S8) |  (Cl2) | |
 (Br2) | |||
 (I2) |
It is also shown in the table that each of these elements exists as a molecule containing two or more of the same atoms joined by a chemical bond. The chemical bonds between atoms of nonmetallic elements are referred to as covalent bonds.
Covalent bonds are electron pairs shared between two atoms.
Single bond - one electron pair
H• + H• combine to
or H:H
Double bond - two electron pairs
Triple bond - three electron pairs
H• + H• combine to
or H:HDouble bond - two electron pairs
Triple bond - three electron pairs
The number of bonds that each of these atoms form in the molecules above can be deduced from the valence electron diagram for that atom as it is equal to the number of unpaired valence electrons.
Note that with the exception of hydrogen, each of the atoms shown has paired electrons. These paired electrons may also be paired on the bonded atom and are referred to as non-bonding electron pairs.
Thus it is possible to predict, for the molecules above, the number of valence electrons involved in bonds and the number that are present as non-bonding electron pairs. The structure of the molecule that this predicts is helpful in understanding both the physical properties and reactivity of the bulk substance.