HISTORY

• Atom


  Tiny sphere that cannot be divided
• Discovery of the electron

  1. JJ Thomson discovered the electron

  2. Atoms have positive charge with negative charges spread throughout (Plum-Pudding model)
• Rutherford's experiment

  1. Fired alpha particles at thin gold foil

  2. Concluded mass of atom concentrated in a nucleus

  3. Proposed electrons orbit the nucleus
• Bohr's model

  1. Atoms emit specific amounts of energy when heated

  2. Electrons in fixed energy levels (shells)

  3. Energy released when electrons fall from high to low energy levels
• Discovery of the neutron

  1. Chadwick bombarded beryllium with alpha particles

  2. Produced unknown radiation

  3. Interpreted as particles with no electrical charge, named neutrons
• John Dalton published table of elements arranged by atomic weights


  1808
• John Newlands published law of octaves


  1864
• Mendeleev's periodic table


  1. Left gaps for undiscovered elements

  2. Rearranged order based on atomic weight

  3. Predicted properties of undiscovered elements
• Periodic table

  • Elements with similar properties in columns (groups)
  • Elements in same group have same number of electrons in outer shell
  • Shell number = Period number, Electrons in outer shell = Group number
• Naming simple compounds


  • Metal name + non-metal name with "ide" ending
  • Metal name + non-metal name + "ate" ending for compounds with oxygen
• Transition metals

  • Located between group 2 and 3
  • High melting and boiling points
  • High density
  • Shiny when polished
  • Malleable
  • Strong
  • Don't break easily
  • Sonorous
  • Ductile
• Outer shell electrons


  Harder to attract and more shielded from nucleus as you go down a group
• Chemical displacement reaction


  One reactant replaces part of another reactant
• Alkaline Metals


  • Na
  • Li
• Reaction of Na with water

  2Na + 2H2O -> 2NaOH + H2
• Reaction of Li with water

  2Li + 2H2O -> 2LiOH + H2
• Alkaline Metals


  • Very reactive
  • Stored in oil
  • Reactivity decreases down the group
• Halogens


  • Group 7 non-metals
  • Form salts
  • Coloured vapours
  • Toxic
• Halogens


  • Have 7 electrons in their outermost shell
  • Need to gain one electron to achieve the stable electronic structure of a noble gas
  • Form covalent bonds with metals
• Reactivity of elements

  Metals are more reactive, non-metals are less reactive
• Halogens exist as diatomic molecules (F2, Cl2, Br2, I2)
• Halogens are poor conductors of heat and electricity