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Allotropy
Allotropy or allotropism is the property of some chemical
elements to exist in two or more different forms, known as
allotropes of these elements. Allotropes are different physical
forms of the same element.
They have almost the same chemical property but different
physical properties.
Allotropy of Carbon1. Diamond
2. Graphite
3. Fullerenes
JGD
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Diamond
All carbons are joined by covalent bonds only.
Hybridisation of carbon : sp3
The formation of such bonds continues in 3D.
109o 28
1.54 Ao
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Properties and Uses :
Property Uses
1. Very Hard due to the strong covalent
bond.
1. Used for cutting and grinding metals,
granites etc.
2. High Melting Point of about 4000oC
because of the strong covalent bond.
2. Diamond drills are used for offshore
drilling as they are strong and
durable.
3. Not conductor of electricity as there
are no free electrons.
3. Jewellery due to dazzling brilliance.
4. Insoluble in water and organic
solvents.
4. Used in surgical tools and other
medical applications.
5. Transparent to radiations like visiblelight, U.V. , X ray etc.
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Graphite
Hybridisation of carbon : sp2
Each carbon forms 3 sigma bonds by using 3 sp2
hybrid orbitals.
This continues on all sides resulting in hexagonalrings.
The remaining p orbital with one electron each is
spread all over the ring.
The formation of such bonds continues in 3D.
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Properties and Uses :
Property Uses
1. Very soft due to the layered
structure which can be slipped over
one another.
1. Used as a lubricant for machine
parts.
2. Good conductor of electricity as
there are free p electrons.
2. Used as electrodes in metallurgy.
3. Unaffected by ordinary solvents like
dil. Acids, alkalies etc.
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Fullerenes
A fullerene is any molecule composed entirely of carbon, in the form of a
hollow sphere, ellipsoid, or tube. Spherical fullerenes are also called buckyballs.
C60-C70 is the usual molecular formula of fullerenes.
Were first isolated from the soot of chimneys.
Buckminster Fullerene
Name comes from architect Richard Buckminster Fuller
C60 is the molecular formula.
Richard Smalley, Robert Curl, James Heath, Sean O'Brien, and Harold Kroto
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Hybridisation : sp2 and sp3
20 six membered rings and 12 five membered rings.