Why do atoms form covalent bonds?

Atoms form covalent bonds to achieve a stable electron configuration, usually a full outer shell, by sharing electrons with other atoms.

Covalent bonding is one of the three primary types of chemical bonding, the other two being ionic and metallic bonding. It is a form of chemical bonding where pairs of electrons are shared between atoms. This type of bonding typically occurs between non-metal atoms which have similar electronegativities.

Atoms always seek to be as stable as possible, and a full outer shell of electrons (usually eight, known as an octet) provides the most stable configuration. This is often referred to as the 'octet rule'. However, not all atoms naturally possess a full outer shell. To achieve this stability, they must either gain, lose, or share electrons. In covalent bonding, atoms choose to share electrons.

For example, consider a molecule of oxygen (O2). Each oxygen atom has six electrons in its outer shell, but it needs eight to be stable. So, each oxygen atom shares two of its electrons with the other, resulting in both atoms having a full outer shell of eight electrons. This sharing of electrons forms a covalent bond, holding the two oxygen atoms together in a molecule of O2.

In summary, covalent bonding is a strategy used by atoms to achieve a stable electron configuration. By sharing electrons, atoms can 'fill up' their outer shell, satisfying the octet rule and achieving maximum stability. This process is fundamental to the formation of many substances and is a key concept in chemistry.