allotropy...

ALLOTROPY

Made by: Abannah, Sneha, Khushboo

Index

05. Graphite

01. Introduction to Allotropy

06. Properties of Graphite

02. Allotropic modifications of Carbon

07. Structure of Graphite

03. Diamond

04. Structure of Diamond

01

INTRODUCTION TO ALLOTROPY

The different forms of elements are called allotropic modifications or allotropes. Allotropes are different structural forms of the same element and possess same chemical behaviours but can exhibit quite different physical properties.

"The existence of two or more different physical forms of a chemical elements are called allotropy."

02

ALLOTROPIC MODIFICATIONS OF CARBON

There are two allotropic forms of carbon:

CRYSTALLINE:

AMORPHOUS:

Amorphous allotropes of carbon are namely:

There are two crystalline forms:

• COAL
• COKE
• LAMPBLACK
• WOOD CHARCOL

• DIAMOND
• GRAPHITE

03

DIAMOND

Uses of Diamond:

Crytalline allotrope of carbon.

• Diamond is mostly used in jewelries for ornamental purpose.
• Industrial diamonds are used on bits of drills and instruments used for cutting glass and metals.

Properties of Diamond:

• Transparent in pure state, however, in the presence of impurities, it exists in various colours.
• Hardest substance known
• high melting point
• Density: 3.51 gm/cm3
• Refractive index: 2.45
• Deficient conductor of electricity and heat.

04

Structure of Diamond

In Diamond each Carbon atom utilizes SP3 hyprid orbitals to form four bonds. Thus, each Carbon atoms are tetrahedrally bonded to four other carbon atoms to give basic tetrahydral unit, which is three dimensionally polymerized to give cubic geometry of the crystal.

Graphite

Crystalline allotrope of Carbon

Properties of Graphite:

• Dark grey crystalline solid
• Dull metalic luster
• Density: 2.2 gm/cm3
• Soft and Greasy to feel
• Adequate conductor of electricity
• Bond length between C- C: 2.42 A°

05

Uses of Graphite:

• Due to greacy property and high melting point, graphite is sutaible to be used as lubricant to reduce friction in machines.
• Used in making electrodes in dray cells and other electrolytic process.
• When mixed with clay, it is used as lead in pencils.

Structure of Graphite

06

• In Graphite, each Carbon atom is trigonally (SP2) hybrid and covalently linked with three other carbon atoms to produce a flat hexagonal ring.
• The hexagonal rings form two-dimensional sheet. These layers are 3.35 A° away from each other and are held together by weak vander waal's forces of attraction.
• The interlayer binding energy is deficient.

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