4.5 Physical Properties in Giant Covalent Substances. Diamond. Structure: Giant covalent macromolecule Bonding: Each carbon atom has 4 bonding pairs of electrons and 0 lone pairs of electrons. According to VSEPR
Structure: Giant covalent macromolecule
Bonding: Each carbon atom has 4 bonding pairs of
electrons and 0 lone pairs of electrons. According to VSEPR
theory in order to minimize the repulsion the 4 pair of
bonding electrons repel each other equally.
Bond angle: 109.5o
No intermolecular forces of attraction, only
intramolecular attractions between the carbon atoms.
The one electron not used in bonding is free / mobile / delocalized and can carry a current.
The weak van der Waals forces between the layers allow them to slide over one another making graphite an excellent lubricant.
The intramolecular covalent bonds between the carbon atoms are too strong to interact with water.
Compared to diamond. This is because of the relatively large amount of space between the layers.
The layers of carbon atoms slide over each other due to weak Van der Waal’s forces between them. When you use a pencil, the layers of carbon atoms are rubbed off and stick to the paper. Graphite is one of the softest substances.
Mpt = 3652°C - 3697°C : b.pt = 4200°C.
Similar to diamond. To melt graphite both the intermolecular van der Waals forces and intramolecular covalent bonds need to be broken.
Not very reactive due to the stability of the carbon-carbon bonds. Chemists have been able to increase the reactivity by attaching active groups to the surface.
Due to the one delocalized electron per carbon atom.
C60 molecules can slide over one another making them softer than diamond but not as soft as graphite
No delocalized valence elections to carry a current because they are all involved in bonding. Called an insulator.
Each silicon atom is held in the lattice by 4 strong covalent bonds, giving it a strong rigid structure.
The intramolecular covalent bonds between the silicon atoms are too strong to interact with water.
Lower than diamond. Si-Si bond is longer than C-C bond in diamond, because Si has a larger radius. As the bond length increases, the amount of energy needed to break the attractive force between the pair of electrons in the covalent bond and the protons in the nucleus decreases.
Properties that make it useful for baking:
Properties that make is useful for breast