Topic 1

• Parts of an atom and their charges

  Proton +1

  neutron 0

  electron -1
• Atomic number


  the number of protons in the nucleus of an atom (bottom)
• mass number


  the sum of the number of neutrons and protons in an atomic nucleus (top)
• Isotopes


  Atoms with the same number of protons but different numbers of neutrons
• compounds


  2 or more elements chemically combined
• mixture


  A combination of two or more substances that are not chemically combined
• what is chromatography done for

  to separate substances in a mixture
• Paper Chromotography


  1) Draw a line in pencil near the bottom of a sheet of filter paper

  2) Add a spot of ink to the line and place the sheet in a beaker of solvent e.g water

  (the solvent used depends on whats being tested)

  4) Make sure the ink isn't touching the solvent or it will dissolve it

  5) Place a lid on top of the container to stop the solvent evaporating

  (each different dye will move up the paper at a different rate)

  (if any of the dyes in the ink are insoluble, they'll stay on the baseline)

  7) When the solvent has nearly reached the top of the paper, take the paper out and leave to dry

  8) the end result is a pattern of spots called chromatogram
• separation tactics


  - filtration

  - evaporation

  - crystallisation
• Filtration practical


  - put filter paper into a funnel and pour mixture in

  - liquid part of mixture runs through the paper, leaving behind a solid residue
• evaporation practical


  - add solution into the evaporation dish

  - gently heat the solution.

  - solvent will evaporate and crystals will form
• what is Distillation


  -separating a mixture when the components of the mixture have different boiling points

  -purifying a liquid
• Distillation practical


  1) solution heated, the part of solution with the lowest BP evaporates first.

  2) vapour cooled, condenses and is collected

  3) rest of solution is left in flask
• distillation problems


  can only separate 2 solutions with very different BP's
• Plum Pudding Model

  
• Plum Pudding Model


  - JJ Thomson

  - 1897

  - showed there was negatively charged ELECTRONS

  - ball of positive charge with negative electrons in it
• Nuclear Model

  
• Nuclear Model


  - Ernest Rutherford

  - 1909

  - ALPHA PARTICLE SCATTERING EXPERIMENTS

  - expected: particles pass through

  - WHAT ACTUALLY HAPPENED: some particles got deflected

  - claimed there was a NUCLEUS AT CENTRE THAT CARRIED MOST OF THE MASS, the rest is mostly empty space.
• Ernest Rutherford results


  - NUCLEUS

  - the rest was empty space
• Bohr's Model

  
• Bohr's Model

  - Neils Bohr

  - 1913

  - suggested electrons were in SHELLS

  - electrons orbit the nucleus in fixed shells
• Mendeleev's periodic table


  - 1869

  - mainly in order of ATOMIC WEIGHT

  - but also based slightly on properties.

  - Left GAPS for what he thought was undiscovered elements.
• Metal's properties


  - strong

  - good heat conductors

  - good electricity conductors

  - high BP and MP
• Transition Metals properties


  - dense

  - strong

  - shiny

  - good conductors
• Group 1


  - 1 electron on outer shell

  - very reactive

  - reactive with water

  - soft

  - low density

  - form +1 ions
• Group 1: going down

  - increase in reactivity

  - lower MP and BP

  - Higher relative atomic mass
• Group 7: Halogens


  - non-metals

  - pairs of atoms

  - form -1 ions
• Group 7: going down

  - less reactive (harder to gain electron)

  - higher MP and BP

  - higher relative atom masses
• Displacement in Halogens


  A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt
• Group 0: Noble gases

  - full outer shell

  - inert (non-reactive)

  - Monatomic gases

  - non-flammable
• Group 0: properties going down


  - BP's increase - this is because of an increase in the number of electrons.