types of substance

• ionic (non metal + metal)

  simple molecular covalent (non metal + non metal)

  giant covalent (diamond, graphite)

  metallic (metals)
• physical properties

  
• ionic compounds


  • strong electrostatic forces so high melting and boiling points
  • solids are rearranged in regular structures with no flow therefore they cannot conduct electricity when solid (ions are in a fixed place)
  • conduct electricity when molten as ions can move
• typical covalent / simple molecular compounds


  • weak forces of attraction meaning low melting and boiling points
  • no delocalised electrons meaning poor conductor of electricity
• graphite and diamond are all different forms of carbon and examples of giant covalent substances
• diamond


  • carbon atom forms 4 strong covalent bonds with other carbon atoms
  • no free electrons as molecule is not charged
  • fixed structure
• graphite


  • entirely of carbon atoms
  • different arrangement
  • three electrons of each carbon form strong covalent bonds, the fourth electron is delocalised
• graphite is used to make electrodes as a lubricant as it can conduct electricity due to its delocalised electron and the layers are slippery and can slide over eachother

  diamond is very hard and can scratch other materials therefore its used in cutting tools
• fullerenes contain 60 carbon atoms covalently bonded to form a cage

  • very strong (covalent bonds)
  • relatively low boiling / melting points due to weak intermolecular forces
• graphene

  • single layer of graphite, one atom thick
  • very strong
  • very light (made up entirely of carbon atoms)
• simple polymers consist of large molecules containing chains of carbon atoms e.g. polyethene
• metals

  • malleable - layers of atoms in metals are able to slide over eachother
  • conduct electricity
  • shiny
• limitations of particular representations and models

  dot and cross

  • doesn't show the structure

  ball and stick

  • shows atoms too far apart

  2-3D

  • doesn't give information about shape of molecule or bond angles involved
• most metals are shiny solids with high melting points, high density and good conductors of electricity

  non-metals have low boiling points and they are poor conductors of electricity