1. Allotropes of Carbon

2. Diamond
Graphite
“Buckyballs” or buckminsterfullerene

3. Different structural/crystalline forms of the same element
Allotrope definition
Different structural/crystalline forms of the same element

4. Diamond
Each carbon atom is bonded to 4 others to form a giant covalent network or lattice

5. Diamond
Each carbon atom is bonded to 4 others to form a giant covalent network or lattice
Is bond is of the same length and equally strong so the carbon atoms are sp3 hybridized

6. Diamond
Each carbon atom is bonded to 4 others to form a giant covalent network or lattice
Is bond is of the same length and equally strong so the carbon atoms are sp3 hybridized
As all the electrons are localised (fixed in position), diamond is exceptionally hard and it does not conduct electricity

7. Diamond
From: ibchem.com/IB/ibnotes/full/bon_htm/14.4.htm

8. Very high melting point Doesn’t conduct electricity Very hard
Properties of Diamond
Very high melting point
Doesn’t conduct electricity
Very hard

9. Graphite
Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings

10. Graphite
Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings
As each bond is the same, the carbon atoms are sp2 hybridised

11. Graphite
Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings
As each bond is the same, the carbon atoms are sp2 hybridised
The remaining p orbital electron is delocalised to form weak bonds between the layers

12. Graphite
Each carbon atom is bonded to 3 other carbon atoms to give layers of hexagonal rings
As each bond is the same, the carbon atoms are sp2 hybridised
The remaining p orbital electron is delocalised to form weak bonds between the layers
The covalent layer lattice has all sigma bonds

13. Graphite
From:

14. Graphite
Because of the layers, graphite is an excellent lubricant as the layers can slide over each other

15. Graphite
Because of the layers, graphite is an excellent lubricant as the layers can slide over each other
Graphite is also a good conductor of electricity because of the delocalised electrons e.g. carbon rods, lead pencils

16. Buckminsterfullerene
Is one member of a family of spherical carbon molecules sometimes called “buckyballs”
Has the formula C60
The C atoms are arranged in hexagons and pentagons to give a geodesic spherical structure similar to a football

17. Buckminsterfullerene
From:

18. Vancouver Geodesic
From:

19. Buckminsterfullerene
Like in graphite, each carbon atom is bonded to 3 others

20. Buckminsterfullerene
Like in graphite, each carbon atom is bonded to 3 others
Each carbon atom is sp2 hybridized

21. Buckminsterfullerene
Like in graphite, each carbon atom is bonded to 3 others
Each carbon atom is sp2 hybridized
There are also delocalized electrons, hence C60 can conduct electricity slightly

22. From: www.nanomaterialsdiscovery.com/technology.php...

23. Silicon Silicon dioxide - SiO2
From: ,

24. Structure of Silicon Silicon contains 4 valence electrons
It forms a lattice similar to that of diamond - each Si atom bonded to 4 others
Silicon is fairly unreactive and acts as an insulator at low temperatures as it has no free electrons
With impurities added it can conduct electricity at low temperatures
From:

25. Structure of silicon dioxide
Commonly known as silica and seen as sand or quartz
Like diamond, SiO2 is also a giant covalent lattice/ structure
Each Si atom is bonded to 4 O atoms, and each O atom is bonded to 2 Si atoms
From: ,

26. Properties of silicon dioxide
has a high melting point - varying depending on what the particular structure is (remember that the structure given is only one of three possible structures), but around 1700°C. Very strong silicon-oxygen covalent bonds have to be broken throughout the structure before melting occurs.
is hard. This is due to the need to break the very strong covalent bonds.
doesn't conduct electricity. There aren't any delocalised electrons. All the electrons are held tightly between the atoms, and aren't free to move
is insoluble in water and organic solvents. There are no possible attractions which could occur between solvent molecules and the silicon or oxygen atoms which could overcome the covalent bonds in the giant structure.