PITE Services: Carbon and its Compounds

Introduction:

Carbon is the most important chemical element (non-metal) in the world having the symbol ‘C’ and atomic number 6. Carbon is most commonly obtained from coal deposits, although it usually must be processed into a form suitable for commercial use. Three naturally occurring allotropes of carbon are known to exist: amorphous, graphite and diamond. Artificially produced graphite is of the alpha type.

Note:

Phase at Room Temperature: Solid

Melting Point: 3823 K (3550°C or 6422°F)

Boiling Point: 4098 K (3825°C or 6917°F)

Atomic Weight: 12.0107

Occurrence in Nature :

· It is present in the earth crust to the extent of 0.02% only in the form of minerals like carbonates, coal, petroleum etc.

· In the atmosphere, it is present in 0.03% in the form of carbon dioxide.

It is useful both in the elemental form and in the combined state with other elements (Hydrocarbons and other compounds).

Uses Of Carbon:

1. All the living things, plants and animals are made up of carbon compounds.

2. A large number of things that we use in our daily life are made of carbon compounds.

3. The materials like cotton, silk, wool and nylon etc., which are used for making clothes are carbon compounds.

Versatile Nature of Carbon:

The Carbon shows the versatile nature due its following property:

The nature of the covalent bond enables carbon to form a large
number of compounds.

1. Catenation: Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. This property is called Catenation. These compounds may have long chains of carbon and branched chain of carbon. No other element exhibits the property of catenation to the extent seen in carbon compounds.

2. Tetravalent: Since carbon has a valency of four other atoms of carbon or atoms of some other mono-valent element. Compounds of carbon are formed with oxygen, hydrogen and many other elements.

3. Small size: Again the bonds that carbon forms with most other elements are very strong making these compounds exceptionally stable. One reason for the formation of strong bonds by carbon is its small size.

v Why does carbon always form a covalent bond?

In the case of carbon, there are four electrons in its outermost shell and needs to gain or lose four electrons to attain noble gas configuration. If it were to gain or lose electrons.

Condition 1: (C^4-anion.)

It could gain four electrons forming C^4-anion. But it would be
difficult for the nucleus with six protons to hold on to ten electrons,
that is, four extra electrons.

Condition 2.

It could lose four electrons forming C⁴⁺cation. But it would require
a large amount of energy to remove four electrons leaving behind a
carbon cation with six protons in its nucleus holding onto just two
electrons. Thus Carbon overcomes this problem by sharing its
valence electrons and hence always forms a covalent bond.

Allotropes of Carbon :

The various physical forms in which an element can exist are
called Allotropes of the element. The carbon element exists in three
solid forms called allotropes. The three allotropes of carbon.

1. Diamond:

Diamond has a three dimensional structure in which each carbon atom is bonded to four other carbon atoms by strong covalent bonds in a tetrahedral manner.

Uses of diamond:

· As precious stone in jewellery.

· For cutting marble stones and other hard materials.

· In drilling equipments.

Structure of Diamond

2) Graphite: In graphite, each carbon atom is bonded to three other carbon atoms in the same plane forming hexagonal rings. Graphite is a good conductor of electricity.

Uses:-

· It is used in making lead pencils.

· As a lubricant in machinery for preventing rusting and friction.

· As an electrodes in dry cells.

3) Buckminster fullerene: It is a new class of carbon allotropes. They are spherical in shape and contain even number of carbon atoms ranging from 60 to 350 or above. This form was discovered by H.W.Kroto, R.F. Curt and R.E.smalley.

Uses:-

· It is used for making drugs to control AIDS.

· It is also used as lubricant and catalysts in laboratories.

· They are used as fibers.

· It is used for making super conductors and semi conductors.

Hydrocarbon and their types:-

Hydrocarbons are the organic compounds which contain only

hydrogen and carbon.

For e.g.:-Methane(CH₄),Ethane(C₂H₆)and ethyne(C₂H₂).

The most important source of hydrocarbon is petroleum.

Types of the Hydrocarbons

i)Saturated hydrocarbons:-

A hydrocarbon in which the carbon atoms are connected by only single bonds is called a saturated hydrocarbon. Saturated Hydrocarbon are also called alkanes. An alkane is a hydrocarbon in which the carbon atoms are connected by only single covalent bonds.

e.g.:- Methane (CH₄), Ethane (C₂H₆)