CHEMISTRY 4.1

CHEMISTRY 4.1

1. THE ATOM

   • John Dalton
     • All matter is made of atoms
     • Atoms are solid spheres
     • Atoms are rearranged in chemical reactions
   • J J Thompson 1897
     • Atoms were not solid spheres
     • Measurements of charge & mass: must contain smaller, -ve particles: ELECTRONS
     • 'Solid sphere' idea changed to 'plum pudding model'
   • Ernest Rutherford 1909
     • Gold foil experiment: expecting +ve particles to be deflected due to 'plum pudding' model
       • However, most particles passed straight through
     • New theory: nuclear atom
       • Tiny +ve nucleus at centre surrounded by a 'cloud' of electrons - lots of empty space
   • Niels Bohr
     • Electrons only exist in fixed electron orbits/shells, not in between
     • Each shell has fized energy
     • Supported by lots of experiments & explained observations

2. THE PERIODIC TABLE

   • DOBEREINER 1828
     • Law of Triads:
       • Found 3 elements with similar properties & grouped them together
   • NEWLANDS 1863
     • Law of Octaves:
       • Every 8th element had similar properties so he listed elements in rows of 7
         • Transition metals broke the pattern
     • Work was criticised:
       • Groups contained elements that didn't have similar properties (i.e. C & Ti)
       • No gaps for undiscovered elements
       • Mixed up metals & non-metals
   • DMITRI MENDELEEV 1869
     • Put elements in order of atomic mass but left gaps unlike Newlands
       • Gaps predicted properties of undiscovered elements
         • Each atomic number was one more than the previous
           • 2 elements in 1st row, 8 in 2nd, 8 in third = electron arrangement

3. TESTING HALIDES

   • Using silver nitrate
     • AgCl = white precipitate
     • AgBr = cream precipitate
     • AgI = yellow precipitate
     • AgNO3 + NaCl --> AgCl + NaNO3

4. TRANSITION METALS

   • CATALYSTS:
     • Iron - Haber Process
     • Nickel = margerine
     • Vanadium (V) oxide = sulphuric acid
   • COMPOUNDS
     • Copper sulphate = blue
     • Potassium permanganate = purple
     • Cobalt chloride = pink
     • Iron (III) oxide = rust