Allotropes, Properties and Structure of Carbon


What is carbon? What are allotropes of carbon? Carbon is an element with the symbol ‘C’ with an atomic number of 6. It can be found in a pure form as graphite or diamond or in an impure form as coal or natural gas.


Origin Of Carbon

Carbon is known for its versatility, it is one of the abundant elements widely distributed in nature. Carbon is the second most abundant chemical in the human body.
‘Carbon’ was derived from the Latin word ‘Carbo’ which means ‘Charcoal’.
The existence of carbon is dated back to 3750BCE, it was first discovered by the Egyptians and Sumerians, but recognized as an element by Antoine Lavoisier in 1789.




Structure of Carbon:

Atomic Structure Of Carbon:

Carbon is made up of 6 electrons and 6 protons in 1 atom. It’s electronic configuration is 2,4 in the K and L shells respectively. Carbon belongs to period 2 and group 4 in the periodic table. It has electronic structures of 1S^2, 2S^2, 2p^2 in the S and P orbitals. It has a valency of 4.


Allotropes Of Carbon:

Allotropes are defined as different forms of an element, which have the same chemical properties but different physical properties.
Carbon has two types of allotropes – The crystalline and non crystalline allotropes. Diamond and graphite are the crystalline or pure forms of carbon. The non crystalline forms are referred to as amorphous or impure forms of carbon.


Differences Between the Crystalline and non crystalline Allotropes of Carbon:

1. The crystalline forms of carbon have definite regular shapes while the non crystalline forms of carbon possess irregular shapes.
2. Crystalline forms of carbon are regarded as the pure forms of carbon while the non crystalline forms of carbon are the impure forms of carbon.
3. The crystalline forms of carbon have high melting point while the non crystalline forms of carbon have low melting point.
4. Crystalline forms of carbon do not easily dissolve in solvents while the non crystalline forms of carbon easily dissolve in solvents.


Crystalline Forms Of Carbon:


Diamond is a pure form of carbon. It is colorless and transparent. It has a density of 3.51gcm^-3. It is regarded as the hardest substance ever known, this makes it useful in glass cutting. Diamonds have a high refractive index which makes it sparkle brightly when it is thoroughly cut and polished.
Diamonds possess an octahedral shape with eight faces bonded together. Within the diamond crystals are millions of carbon atoms arranged in a network manner. Each carbon atom in diamond is bounded to four others. Each of the carbon atom is Sp^3 hybridized.
Diamonds are poor conductors of electricity.



Graphite is another pure form of carbon. It occurs naturally in places like Korea and Germany. It is planar hexagonal, it comes out as rods and bars. Each carbon atom is Sp^2 hybridized. Graphite is very slippery or greasy to touch. Graphite though a non metal, conducts electricity.


Amorphous Forms Of Carbon:

1. Coal:

Coal is formed underneath stratified rocks by the decayed plant fragments like dead wood, branches and leaves which have laid beneath the rock for millions of years.
Coal is used as fuel for locomotives in power stations to generate electricity.


2. Charcoal: There are three common types of charcoal:

– Wood charcoal:
Wood charcoal is obtained by heating woods in absence of air. This process of heating wood is known as destructive distillation of wood. The products obtained from destructive distillation of wood are used as fuels.

– Animal charcoal:
Animal charcoal is obtained by heating fat free animal bones in the absence of air, it is a good adsorbent i.e it adsorbs color from coloring materials in a solution.

– Sugar charcoal:
Sugar charcoal is made by heating pure sugar using concentrated tetraoxosulphate(VI) acid.


3. Lampblack or Black Soot:

Black soots are obtained from burning kerosene. It is gotten from the lantern we use at home. It is used as black pigment in printing ink, shoes polishes etc.


Properties Of Carbon:

Physical Properties:

1. Carbon is either soft i.e in graphite or hard i.e in diamond.
2. Carbon in diamond has a shiny appearance and a dull gray or black appearance in graphite.
3. The atoms of carbon can be bounded in different ways.
4. The allotropes of carbon have different structures.


Chemical Properties:

1. Combustion reaction: Carbon dioxide, heat and light are produced when carbon burns in air, this is called combustion reaction.
2. Oxidation reaction: The presence of oxygen is needed for the oxidation of carbon and it’s compounds.
3. Addition reaction: This reaction occurs when two or more reactants combine to form a product.
4. Substitution reaction: In this reaction a functional group is replaced by another functional group.


Applications and Uses Of Carbon:

1. Carbon in the form of diamond is used in jewellery making.
2. Ink paints are gotten from the amorphous forms of carbon.
3. Pencils are made from graphite, one of the pure forms of carbon.
4. Fuels are made from coal etc.


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