C2

• Dmitri Mendeleev

  • Created first proper periodic table 1869
  • Put ~50 elements into the periodic table in order of atomic mass
  • Kept elements with similar properties in the same group vertically
  • Left gaps which would hold other elements when discovered
• Current periodic table

  • Orders based on atomic number but fits Mendeleev’s patterns
  • Groups correspond to number of electrons in outer shell
• Ionic bonding


  Ions form when an atom loses or gains electrons

  Ionic bonding is when two ions with opposite charges (eg -2 and 2+) bond together by electrostatic forces
• Ionic compounds 


  Shown using dot cross diagrams

  Regular lattice structure (closely packed with strong electrostatic forces between oppositely charged ions)

  High melting and boiling points (uses lots of energy to break down)

  Don’t conduct electricity (ions are fixed in place and can’t move when solid)

  Easily dissolve in water and will carry an electric charge
• Covalent bonds


  Non metal atoms form covalent bonds by sharing electrons to have a full outer shell

  Each bond provides one shared electron

  Electrostatic attraction between nuclei and electrons

  Simple molecular structures using very strong covalent bonds

  Low melting and boiling points (weak forces of attraction)

  Liquid or gas (mostly) at room temperature

  Don’t conduct electricity
• Diamond


  Each carbon atom forms 4 covalent bonds in a rigid structure to make it really hard

  High melting point

  Doesn’t conduct electricity (no free electrons)
• Graphite 


  Black and opaque

  Each carbon atom forms 3 covalent bones to form sheets of carbon atoms that can slide over each other (lubricant)

  High melting point

  Conducts electricity due to delocalised electrons that can move
• Graphene


  Single sheet of graphite

  Extremely strong covalent bonds

  So thin it is translucent

  Better than graphite at conducting electricity due to completely free delocalised electrons
• Fullerene


  Large carbon moleculesLarge carbon molecules

  Shaped like tubes or hollow balls

  Different fullerenes have different numbers of carbon atoms

  Atoms arranged in rings with delocalised electrons

  Melting and boiling points are relatively high due to more intermolecular forces
• Polymers


  Formed when small molecules (monomers) join together, this reaction is called polymerisation

  In polymer chains strong covalent bonds hold atoms together

  Weak forces are only held together by weak intermolecular forces that slide over each other. They can be stretched easily and have a low melting point

  Strong forces have covalent bonds which have higher melting points, are rigid and can’t be stretched.
• Properties


  Properties of types of material depend on bonds and structures

  Individual atoms in materials don’t have properties themselves
• Metallic bonding

  All metals have the same basic properties due to layers of metal ions with free delocalised electrons in between

  Electrostatic attraction
• Metal properties


  Hard, dense, and lustrous (shiny)

  Strong attraction between delocalised electrons and positive ions

  High melting and boiling points

  Malleable (hammered into shapes) but also strong and hard

  Good conductors of heat and electricity

  React with oxygen to form metal oxides

  Can form alloys (metal with better properties)