Giant Molecular Structures
| Properties | Diamond | Graphite |
| Structure | All carbon atoms connected to each other by very strong covalent bonds in a 3 dimensional structure.Each carbon atom is bonded to 4 other carbon atoms by very strong covalent bonds.
Also applicable to SiO2. | Flat layers of carbon atoms. Each carbon atom is connected to 3 other atoms by strong covalent bonds in a 2 dimensional hexagonal structure. |
| Electrical conductivity | Diamond does not conduct electricity Each carbon atom uses up its 4 valence electrons for bonding with 4 other carbon atoms. No free electrons to move and conduct elec. | Graphite can conduct electricity In each layer, a carbon atom is bonded to 3 other carbon atoms, leaving 1 valence electron free. These electrons are delocalized, can travel along the layers, and conduct electricity.
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| Hardness or softness | Giant molecular structure held together by very strong covalent bonds. A lot of energy required to break all these bonds hence diamond is hard. | Consist of layers of carbon atoms held together by very strong covalent bonds.Attractive forces between layers is weak, hence layers can slide past one another, making graphite soft.
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| Melting point | Very high melting point Structure Giant molecular structure with millions of carbon atoms held together by very strong covalent bonds.
A large amount of energy is needed to break these bonds -> high m.p. | Very high melting point. Layers of carbon atoms held together by strong covalent bonds. A lot of energy needed to break these bonds -> high m.p. |