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Chemical BondingChemical Bonding
Brief RecapBrief Recap
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Substances
Metallic substances
Ionic Compounds
Covalent Substances
Simple Molecular Substances
Simple Molecular Substances
Giant Molecular Substances
Giant Molecular Substances
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Giant Molecular Giant Molecular SubstancesSubstances
MacromoleculesMacromolecules
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GiantsGiants
How about giantgiant molecular structure?
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GiantGiant metallic structure GiantGiant ionic structure
Structure of Giant Molecular Structure of Giant Molecular Substances (In general)Substances (In general)
• Giant covalent structure
• Atoms held by strong covalent bonds
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Giant Molecular SubstancesGiant Molecular Substances
www.diamondvues.com/loose_diamond_shapes/
http://chemistry.about.com/od/periodictableelements/ig/Element-Photo-Gallery.--98/Graphite.htm
mrbarlow.wordpress.com/2008/02/12/sandcastles
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DiamondDiamond
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• Physical properties
Melting/Boiling Point
Hardness
Electrical conductivity
Solubility in water Insoluble
DiamondDiamond
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Very high
Very hard
Does not conduct
www.diamondvues.com/loose_diamond_shapes/
DiamondDiamond
• Structure: Giant covalent structure
9http://www.uwgb.edu/dutchs/petrolgy/Diamond%20Structure.HTM
Carbon atoms
Covalent bonds
DiamondDiamond
• Structure: Giant covalent structure
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Each carbon atom joined tetrahedrally to four other carbon atoms by strong covalent bonds.
DiamondDiamond
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Physical Properties Rationales
Very high melting/boiling point
Very hard
Does not conduct electricity
A lot of energy is required to break the strong covalent bonds between the carbon atoms.
No mobile charge carriers (ions or electrons) present.
DiamondDiamond
Uses Rationales
Drill-tips and cutting tools
Gemstones in jewellery –
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It is very hard.
http://www.supertoolscompany.com/F7948/diamond_cutting_tools.html
http://www.jewelsdeparagon.com/catalog/product_info.php?products_id=1092
GraphiteGraphite
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GraphiteGraphite
• Physical Properties
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http://chemistry.about.com/od/periodictableelements/ig/Element-Photo-Gallery.--98/Graphite.htm
Melting/Boiling Point
Hardness
Electrical conductivity
Solubility in water Insoluble
Very high
Soft and slippery
Conducts
GraphiteGraphite
• Structure: Giant covalent structure
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Microscopic image of graphite
http://www.physik.uni-augsburg.de/exp6/imagegallery/afmimages/afmimages_e.shtml
http://www.pbase.com/beekeeper/image/23669013
Honeycomb
GraphiteGraphite
• Structure: Giant covalent structure
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Carbon atoms in one layer
http://www.chemguide.co.uk/atoms/structures/giantcov.html
Layers of carbon atoms
http://www.scifun.ed.ac.uk/card/flakes.html
Carbon atoms
Covalent bonds
Van der Waals’ forces
GraphiteGraphite
• Structure: Giant covalent structure
• Consists of flat layers of carbon atoms
• In each layer, each carbon atom joined to three other carbon atoms by strong covalent bonds.
• Layers of carbon atoms are held by weak van der Waals’ forces.
• No covalent bonds between the layers.
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GraphiteGraphitePhysical Properties Rationales
Very high melting/boiling point
Soft and slippery
Conducts electricity
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A lot of energy is required to break the strong covalent bonds between the carbon atoms within each layer.Layers of carbon atoms can slide over each other due to the weak van der Waals’ forces between the layers.
Each carbon atom contributes one outer shell electron which is not used to form covalent bonds. These electrons can move along the layers to conduct electricity.
GraphiteGraphite
Uses Rationales
Dry lubricant
Pencil lead
Inert electrodes for electrolysis
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It is slippery and does not decompose at high temperatures.
It is soft as the carbon layers can flake off easily.
It is a good conductor of electricity and is fairly unreactive.
Diamond and GraphiteDiamond and Graphite
• Different forms of carbon– Allotropes of carbon
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Allotropes are different forms of the same element.
Allotropes are different forms of the same element.
SandSand
Silicon (IV) oxide/silicon dioxide/silicaSilicon (IV) oxide/silicon dioxide/silica
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• Physical properties
Melting/Boiling Point
Hardness
Electrical conductivity
Solubility in water Insoluble
SandSand
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Very high
Very hard
Does not conduct
mrbarlow.wordpress.com/2008/02/12/sandcastles
SandSand
• Structure: Giant covalent structure
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http://www3.moe.edu.sg/edumall/tl/digital_resources/chemistry/images/img_CH_00019.jpg
Each silicon atom is covalently bonded to four oxygen atoms by strong covalent bonds in a tetrahedral structure and each oxygen atom is covalently bonded to two silicon atoms.
SandSand
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Physical Properties Rationales
Very high melting/boiling point
Very hard
Does not conduct electricity
A lot of energy is required to break the strong covalent bonds between the carbon atoms.
No mobile charge carriers (ions or electrons) present.
