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Carbon is an element that is the found in abundance in the earth's crust. It is found in

group 14 of the Periodic Table and has the atomic number 6. Carbon, which is non

metallic in nature, is the 4th most abundant element in the universe and the 1th most

abundant element in the !arth's crust. Carbon is such an important element that an

entirel" separate field of chemistr" is devoted to this element and its compounds.

#rganic chemistr" is the stud" of carbon compounds.

How carbon was discovered

$umans have been aware of carbon since the earliest of times. %hen cave peoplemade a fire, the" saw smo&e form. The blac& color of smo&e is caused b" unburned

spec&s of carbon. The smo&e ma" have collected on the ceiling of their caves as soot.

ater, when lamps were invented, people used oil as a fuel. %hen oil burns, carbon

is released in the reaction, forming a soot" covering on the inside of the lamp. That

form of carbon became &nown as lampblac&. ampblac& was also often mi(ed with

olive oil or balsam gum to ma&e in&. )nd ancient !g"ptians sometimes used

lampblac& as e"eliner.

#ne of the most common forms of carbon is charcoal. Charcoal is made b" heating

wood in the absence of air so it does not catch fire. Instead, it gives off water vapor,

leaving pure carbon. This method for producing charcoal was &nown as earl" as the

*oman civili+ation - /.C.0).. 4263.

rench ph"sicist *en5 )ntoine Ferchault Reaumur (1683-1757) believed carbon

might be an element. $e studied the differences between wrought iron, cast iron, and

steel. The main difference among these materials, he said, was the presence of a

blac& combustible material that he &new was present in charcoal.

Carbon was officiall" classified as an element near the end of the eighteenth

centur". In 1272, four rench chemists wrote a boo& outlining a method for naming

chemical substances. The name the" used, carbone, is based on the earlier atin term



for charcoal, charbon.

Coal, soot nearl" pure carbon3, and diamonds are all nearl" pure forms of carbon.

Isotopes

Carbon e(ists in three naturall"0occurring isotopes 8 carbon019, carbon01:, and

carbon014; the numbers refer to their atomic weights. The different &inds of carbon

have ver" similar but not <uite identical3 chemical and mechanical properties; the

main practical significance of the e(istence of different isotopes stems from the fact

that carbon014 is radioactive, with a half0life of a few thousand "ears. This is what

ma&es carbon dating possible 8 C014 is thought to be created b" impacts from cosmic

ra"s at around the same rate it disappears through radioactive deca", so the ratio of the

isotopes in the environment should sta" more or less constant. iving organisms

constantl" e(change carbon with their environment until the da" the" die 8 so if we

find a s&ull with onl" half as much C014 in it as we see in our environment, we can

infer that its owner died one half0life of C014 ago 8 that=s about ,6-- "ears. The

techni<ue is e(tremel" useful in archaeolog", but it is hard to &now <uite how

accurate it is 8 the assumption that C014 levels in the atmosphere have remained

appro(imatel" constant is a difficult one to test.

3.0 Properties to their usage in everyday life as is in industry



3.1 How carbon is essential to life

>ost living things on !arth are made of carbon. iving things need carbon in order

to live, grow, and reproduce. Carbon is a finite resource that c"cles through the !arth

in man" forms. This ma&es carbon available to living organisms and remains in

balance with other chemical reactions in the atmosphere and in bodies of water li&e

ponds and oceans.

In its metabolism of food and respiration, an animal consumes glucose C6$19#63,

which combines with o("gen #93 to produce carbon dio(ide C#93, water $9#3,and energ", which is given off as heat. The animal has no need for the carbon dio(ide

and releases it into the atmosphere. ) plant, on the other hand, uses the opposite

reaction of an animal through photos"nthesis. It inta&es carbon dio(ide, water, and

energ" from sunlight to ma&e its own glucose and o("gen gas. The glucose is used for

chemical energ", which the plant metaboli+es in a similar wa" to an animal. The plant

then emits the remaining o("gen into the environment.

Cells are made of man" comple( molecules called macromolecules, which include

proteins, nucleic acids *?) and ?)3, carboh"drates, and lipids. The

macromolecules are a subset of organic molecules an" carbon0containing li<uid,

solid, or gas3 that are especiall" important for life. The fundamental component for all

of these macromolecules is carbon. The carbon atom has uni<ue properties that allow

it to form covalent bonds to as man" as four different atoms, ma&ing this versatile

element ideal to serve as the basic structural component, or bac&bone, of the

macromolecules.



Diamond

iamonds are formed inside the earth under the conditions of high temperature

about 1--oC3 and high pressure about 2-,--- atmospheres3. In a diamond cr"stal,

each carbon atom is lin&ed to four other carbon atoms b" covalent bonds in a

tetrahedral fashion. This results in a three dimensional arrangement as shown in Fig.

!.1

Fig. 28.1 Three dimensional networ o! car"on atoms in diamond

The three0diamensional networ& of covalentl" bonded carbon atoms provides a

rigid structure to diamonds. This rigidit" ma&es diamond a ver" hard substance.

It is, in fact, the hardest natural substance &nown. The onl" other substance harder

than diamond is silicon carbide which is also &nown as carborandum but note that

diamond is a natural substance whereas carborandum is a s"nthetic one.

iamonds are basicall" colourless. $owever, some impurities impart colour to

them.

The densit" of diamond is high. It has a value of :.1 g cm8:. The melting point

of diamond in vacuum3 is also ver" high, i.e. :--oC because a large amount of

heat energ" is re<uired to brea& the three0dimensional networ& of covalent bonds.

@ince all the four electrons are covalentl" bonded and there are no free electrons in

diamond, hence it does not conduct electricit". /ut diamond is a good conductor of

heat. Its thermal conductivit" is five times that of copper. Thus, it can easil"



dissipate the heat energ" released b" friction when it is used as an abrasive.

/ecause of its above0mentioned properties, diamond has the following usesA

i3 It is used in cutting and grinding of other hard materials.

ii3 It is also emplo"ed in instruments used for cutting of glass and drilling of

roc&s.

iii3 It is used in Beweller". /eautiful ornaments are made with diamonds. The

high refractive inde( of diamond 9.3 ma&es it ver" brilliant when it is

properl" cut and polished.

"raphite

In contrast to diamond, graphite is soft, blac& and slipper" solid. It has a metallic

luster. It is also a good conductor of electricit" and heat.

/oth graphite and diamond contain onl" carbon atoms, then wh" do the" e(hibit

such different properties %e can find an answer to this <uestion if we loo& at the

structure of graphite as given below in ig.97.9.

Covalent bond Carbon atom

#tructure of Diamond #tructure of "raphite

Fig.28.2 #tructures o! $iamond and gra%hite

carbon atoms

wea$ binding forces

%ovalentbond

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