All organic life on earth is carbon-based. The quantity or the amount of carbon in nature is quite small, yet it forms the most complex array of compounds from diamonds to DNA.
The uniqueness of carbon among all the elements owes to its electronic configuration. It has the atomic number 6. Two electrons fill the inner orbit and four electrons occupy the outer orbit. It requires four electrons to fill its octet, giving it a valency of four.
The unique properties of carbon that makes it the most versatile element on earth can be attributed to its:
Given its small size, the hold of the carbon nuclei on the electron helps it form strong stable bonds with other elements.
As mentioned earlier, carbon needs four electrons to fulfil its octet, accepting four electrons would lead to four negative charges on the atom which would make it a very unstable system. Carbon extensively forms covalent bonds with other elements to satisfy its octet requirement.
In a covalent bond, two atoms would come together to share their electron and an effective sharing at an optimum distance will form a bond. This property allows carbon to form four bonds with four monovalent elements at one time. The size helps it hold on to the shared pair of electrons and it goes on to form covalent bonds with a wide range of elements such as hydrogen, oxygen, nitrogen, sulphur, chlorine etc.
Carbon is the only atom that can form long chains with numerous architectures. The self-linking property of carbon atoms is known as catenation. One carbon can at most form a bond with four other carbons, each of which can propagate the chain by linking to other carbon while satisfying its tetravalency. This rudimentary binding format creates the hardest compound on earth - diamond.
The catenating ability of carbon is successful primarily due to its small size, which avoids severe steric clashes between the atoms. Catenation is also observed in silicon but is not as extensive as in carbon, because its size is bigger than carbon and it has a more diffused electron cloud, which causes electronic repulsion with adjacent atoms.
Carbon forms long chains by linking with each other, the chains can be linear, but there can also be branches. Carbon atoms can also be arranged in cyclic rings. Apart from single bonds, carbon can also form double and triple bonds. The multiplicity of bonds helps carbon form compounds with other elements like nitrogen and oxygen.
Carbon compounds have another interesting feature of isomerism. Isomers are compounds that have the same molecular formula but different structures, which means the same number of atoms can be arranged in multiple ways to have a different structure with different properties.
This gives carbon compounds tremendous versatility.
Some Unique Classes of Carbon Compounds
Carbon compounds with at least one metal bond are called organometallic compounds. Examples: Ferrocene, Zeise's Salt, and tetraethyl lead.
Carbon forms a binary compound with another lower electronegativity element called carbides. Examples: CaC2 , Al4C3 , SiC , TiC.
Carbon-containing bonded halogens are called Carbon Halides. Example: CCl4 (carbon tetrachloride), CI4 (carbon tetraiodide).
Molecular clusters made up of carbon and boron atoms form a unique class of compounds called Carboranes. Example H2C2B10H10.
Carbon is used in the form of fossil fuel and crude oil.
Carbon is used in the form of petrochemical products.
Carbon is used to form various commercial polymers, such as plastics, which are synthetic carbon polymers.
Carbon steel which is a carbon alloy with iron is used to produce high-strength wires and machines.
Carbon allotrope graphite mixed with clay is used to form lead that is used to make pencils.
Carbon allotrope diamond is used as a gem, and in industry, it is utilised in cutting and polishing tools.
Carbon black is used in the printing ink, carbon papers, and in rubber products.
Activated Charcoal is used in filters as an absorbent and adsorbent material, which can filter toxins.
More than one million compounds of carbon are known so far.
Carbon has a large number of allotropes, the most familiar of them are diamond and graphite. New allotropes of allotropes carbon such as fullerene (C60) and Graphenes have been discovered in recent decades.
Carbon is the basis of all life.
Carbon has an atomic number of 6.
Carbon has a valency of four (Tetravalency).
Carbon can link with other carbon atoms to form large chains. This is called catenation.
Carbon can form multiple bonds (double and triple).