Types of Covalent Bonds
Single Bond
Hydrogen Molecule
Hydrogen atom has only one electron in its outermost shell, and requires one more electron to acquire the nearest noble gas configuration of helium (He:1s2). To do so, two hydrogen atoms contribute one electron each to share one pair of electrons between them. This leads to the formation of a single covalent bond between the two hydrogen atoms.
Double Bond
Oxygen Molecule
An oxygen atom has six electrons in its valence shell. As a result, it requires 2 more electrons to achieve the nearest noble gas configuration. When two oxygen atoms share two pairs of electrons this is achieved:
Triple Bond
Nitrogen Molecule
Nitrogen atom has five electrons in its valence shell. It requires three more electrons to acquire a stable configuration of the nearest noble gas (neon). This is done by mutually sharing three pairs of electrons as shown below.