Two oxygen atoms may achieve stability by forming covalent bonds with one another. Each oxygen atom has six electrons in its outer shell. To become stable, the two atoms share two pairs of electrons, forming molecular oxygen. When two pairs of electrons are shared (0=0), the bond is called the double covalent bond. Some atoms form triple bonds with one another by sharing three pairs of electrons. For example, nitrogen form a triple covalent bond, by sharing three pairs of electrons with another.
