Carbon and its Compounds

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.

Chlorine Molecule
Chlorine atom has seven valence electrons. Thus, each Cl atom requires one more electron to acquire the nearest noble gas configuration (Ar:2, 8, 8). This they do by mutual sharing of one pair of electrons as shown below.

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.

Activity
Show how nitrogen shares a covalent bond with hydrogen in the formation of ammonia (NH₃). Are all electrons involved in the bonding? Give the Lewis structure of the covalent bond also.

Suggested Answer

The electronic configurations of nitrogen and hydrogen are

Thus, each nitrogen atom requires three more electrons to acquire a stable noble gas configuration. On the other hand, each H-atom requires only one electron to achieve the stable helium configuration. This is done by mutually sharing three pairs of electrons between one nitrogen and three hydrogen atoms, as shown below.

The unshared pair of electrons on the nitrogen atom (in ammonia molecule) is not involved in bond formation and is called a lone pair of electrons.