Allotropic forms of carbon

Carbon exists in different forms
crystalline forms of carbon are explained in this presentation.

1. Allotropic Forms of Carbon Chap # 4 p-Block Elements XII Chemistry Ms. Sidra Javed

2. Allotropy - The existence of an element in more than one forms

3. Allotropes - the different forms are called as allotropes

4. Allotropes of an element - chemically same but different physical properties

5. Allotropic forms of Carbon

6. Allotropic forms of carbon Crystalline forms Diamond Graphite Fullerene Amorphous forms Coal Charcoal Coke Lamp black etc

7. FULLERENE DIAMOND GRAPHITE

8. DIAMOND

9. Structure Each C-atom is covalently bonded to four other C-atom i.e. sigma bonds - Tetrahedral unit Sp 3 -hybridization C-C-C bond angle = 109.5 O C-C bond length = 1.54A O C-C bond energy = 347 kj/mol

10. Properties In diamond each C-atom utilizes its four unpaired electrons in bond formation. These bonding electrons are localized. Due to this reason diamond is a bad conductor of electricity.

11. Properties Diamond is the hardest substance ever known. Pure diamond is colorless. Due to impurities it may be colored Its melting point is 3500 O C. Pure diamond is transparent to x-rays. It has high refractive index i.e. 2.45. Its density is 3.5 gm/cm 3

12. GRAPHITE

13. Structure Sp 2 hybridization Each carbon is bonded with 3 other carbons atoms via sigma bonds Fourth electron of each c-atom forms delocalized p-system. Hexagonal rings in parallele layers Bond angle = 120 O C-C bond length = 1.42A O . Distance between layers = 3.35A O weak van der waals forces These layers can slide over one another.Thus it is very soft.

14. Properties It is dark gray, have dull metallic luster. It is soft and greasy. Density is 2.2 gm/cm 3 . It is used in the preparation of electrodes as it conducts electricity, as moderator in nuclear reactors and as a lubricant.

15. End of Lesson. Any Questions?