This document discusses carbon and its importance in daily life. It notes that carbon is the basis of all known life and is the fourth most abundant element in the universe. Carbon has unique properties that allow it to form many different organic compounds and polymers. It can bond with itself and other elements through covalent bonding, forming long chains and complex structures. Some key allotropes and forms of carbon discussed include diamond, graphite, amorphous carbon, and fullerenes.

2. We are surrounded by compounds made up of carbon and its
substituents. The list given below illustrates the importance of
carbon compounds in our daily life.
1. Foods [starch, sugar, fats, vitamins, proteins]
2. Fuels [wood, coal, alcohol, petrol]
3. Household and commercial articles [paper, soap, cosmetics,
oils, paints]
4. Textile fabrics [cotton, wool, silk, linen, rayon, nylon]
5. Drugs and disinfectants [penicillin, quinine, aspirin, sulfa
drugs]
6. Poisons [opium, strychnine]
7. Perfumes [vanillin, camphor]
8. Explosives [nitroglycerine, dynamite, picric acid, TNT]
9. Dyes [indigo, congo red, malachite green]
10. War gases [mustard gas, chloropicrin, lewisite]

3. Carbon is the 15th most abundant element in the Earth's crust,
and the fourth most abundant element in the universe by mass
after hydrogen, helium, and oxygen. It is present in all known
life forms, and in the human body carbon is the second most
abundant element by mass (about 18.5%) after oxygen.
This abundance, together with the unique diversity of organic
compounds and their unusual polymer-forming ability at the
temperatures commonly encountered on Earth, make this
element the chemical basis of all known life.

4. Carbon is the chemical element with symbol C and atomic
number 6. The electronic configuration of carbon atom is [He]
2s2 2p2. So valence shell (outermost shell) of carbon atom
contains 4 electrons.
According to Octate rule, Valence shell should have 8
electrons. So in order to complete octate either carbon will
accept 4 electrons or will loss 4 electrons.
C + 4e- C4- ……….(1)
C C4+ + 4e- ……….(2)

5. But this two are not possible. Carbon’s valence shell already
contain 4 electrons and because of small size of carbon if we
add another 4 electrons, there will be electronic – electronic
repulsion that won’t allow carbon to accept 4 electrons. So
this process is not possible.
In another process carbon losses 4 electrons. As we know,
size of carbon is small and it contains 4 electrons in its
valence shell, therefore attraction force between nucleus and
electrons won’t allow carbon to loss 4 electrons.

6. Carbon overcomes this problem by sharing its valence
electrons with other atom of carbon or with atoms of other
elements through covalent bonding.

7. Self combination or Catenation- Catenation is the
linkage of atoms of the same element into longer chains.
Catenation occurs most readily in carbon, which
forms covalent bonds with other carbon atoms to form longer
chains and structures. Carbon exhibits catenation to
maximum extent because of strong carbon-carbon bond and
tetracovalency.

8. Occurrence of Carbon- Carbon exists in two states in
nature.
Free state- Compound containing only carbon atom, not any
other element.
For eg.- Graphite, Diamond, Fullerene
Combined state- Carbon combine with other element to form
compound.
For eg.- CO2, C8H18 (Octane), C12H22O11(Sugar), MgCO3,
CaCO3

9. Allotropes of carbon - An element, in different forms,
having different physical properties but similar chemical
properties is known as allotropy. Carbon shows allotropy.
Such different forms are called 'allotrope' of an element or
allotropic forms.
There are three well known allotropic forms of carbon and
they are amorphous carbon, diamond and graphite. The fourth
allotropic form of carbon is buckminsterfullerenes which is
basically an artificial form of carbon and is made up of 60 C
atoms.

10. A few examples of pure carbons are as follows:
Coal, Coke, Charcoal (or wood charcoal), Animal Charcoal (or
bone black), Lamp black, Carbon black, Gas carbon and
Petroleum coke.
In diamond, each carbon atom is bonded to four other carbon
atoms forming a rigid three-dimensional structure.

11. In graphite, each carbon atom is bonded to three other carbon
atoms in the same plane giving a hexagonal array. One of these
bonds is a double-bond, and thus the valency of carbon is
satisfied. Graphite structure is formed by the hexagonal arrays
being placed in layers one above the other.

12. These two different structures result in diamond and graphite
having very different physical properties even though their
chemical properties are the same. Diamond is the hardest
substance known while graphite is smooth and slippery.
Graphite is also a very good conductor of electricity unlike
other non-metals.
Diamonds can be synthesised by subjecting pure carbon to
very high pressure and temperature. These synthetic
diamonds are small but are otherwise indistinguishable from
natural diamonds.

13. Diamond Graphite
It occurs naturally in free state.
It occurs naturally and is manufactured
artificially.
It is the hardest natural substance
known.
It is soft and greasy to touch.
It has high relative density (about 3.5). Its relative density is 2.3.
It is transparent and has high
refractive index (2.45).
It is black in color and opaque.
It is non-conductor of heat and
electricity.
Graphite is a good conductor of heat
and electricity.
It burns in air at 900°C to give CO2. It burns in air at 700-800°C to give CO2.
It occurs as octahedral crystals. It occurs as hexagonal crystals.
It is insoluble in all solvents. It is insoluble in all ordinary solvents
Comparison of the Properties of Diamond and Graphite

15. Fullerenes form another class of carbon allotropes. The
first one to be identified was C-60 which has carbon
atoms arranged in the shape of a football. Since this
looked like the geodesic dome designed by the US
architect Buckminster Fuller, the molecule was named
fullerene.