Chemistry

• metallic bonding is the electrostatic attraction between positive metal ions and negative delocalised electrons (opposite charges attract)
• properties of metallic structures

  high boiling and melting point, conductors, soft, shiny, malleable
• Alloys are mixtures of two or more elements 


  Stronger and harder than normal metals, contain different sizes of atoms that disrupt regular pattern, layers can’t slide
• mild steel - 0.2% carbon

  medium steel - 0.3-0.6% carbon

  stainless steel - 12-25% chromium

  high carbon steel - 0.6-1.5% carbon
• covalent bonding is when non metals share a pair of electrons to fill their outer shells
• properties of simple covalent molecules

  low boiling point, do not conduct electricity
• simple covalent molecules

  molecules containing few atoms joined by covalent bonds
• graphite

  carbon atoms, 3cc bonds, no layer bonds, 1 delocalised electron, conduct electricity, lubricant (layers slide), high melting point, used in pencils
• diamond

  carbon atoms, 4cc bonds, tetrahedra, very high melting and boiling point, hard, strong, doesn’t conduct electricity, used in: blades and jewellery
• silica dioxide

  4cc, tetrahedral, small, semi-conductor, high melting point, transistors, electronics
• graphene

  single sheet of graphite, flexible, tough, hexagonal lattice, 3cc bonds, very thin
• ionic bonding is the transfer of electrons between metals and non-metals (oppositely charged ions are held together by strong electrostatic forces of attraction)
• ionic bonding

  metals loose electrons to become positive ions, non-metals gain electrons to become negative ions (to gain full outer shells)
• ionic bonding properties

  high melting point, conduct when aqueous/molten, dissolve easily in water
• buckminsterfullerene-

  • 3 covalent bonds
  • 60 atoms (C60)
  • giant molecule
  • low melting point
  • ball (lubricant)
  • nanotech / electronics
• crude oil

  H- heated

  E- evaporate

  R- rises

  C- condenses

  • concentration gradient
  • smaller chain lengths condense at top (lowest boiling point)