f. y. b. sc. chapter bonding sem i

8/3/2019 F. Y. B. Sc. Chapter Bonding Sem I

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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



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



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.



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.



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.



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



Hybridisation : sp2 and sp3

20 six membered rings and 12 five membered rings.

f. y. b. sc. chapter bonding sem i

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