Carbon and its Compounds

Although there are more than hundred elements around us we do not find these elements in their native form in nature. This is because most of these elements are highly reactive. They interact with each other to form simple or complex substances. Only elements with the noble gas configuration have no tendency to react further since they have completely filled outermost electronic configuration of their orbitals or shells. An electronic structure of this type gives stability to an element, making it less reactive. Most elements do not have a noble gas configuration and consequently aim to achieve it. They attain this configuration by combining with each other either by gaining or loosing energy. The chemical reactivity of any element is consequently related to the number and distribution of electrons in its atom and the energy changes involved therein. The lower the energy of a system, the greater is its stability. Hence, any change that gives the elements extra stability by loosing and gaining energy occurs spontaneously.

In the previous chapter one has observed the formation of a chemical bond by the transfer of electrons called the ionic bond. Atoms also acquire the stable noble gas configuration of having eight electrons in the outermost shell (called the octect rule) by mutual sharing of one or more electrons. When the chemical bond occurs by mutually sharing of electrons it is called covalent bonding.

Covalent Bond
A covalent bond is defined 'as the force of attraction arising due to mutual sharing of electrons between the two atoms.' The combining atoms may share one, two or three pairs of electrons. The covalent bond is formed between two similar or dissimilar atoms by a mutual sharing of electrons, which are counted towards the stability of both the participating atoms. When the two atoms combine by mutual sharing of electrons, each of the atoms does so, in order to acquire stable configuration of the nearest noble gas. A small line (-) between the two atoms is represents a covalent bond. The compounds formed due to covalent bonding are called covalent compounds.