Topic 1 - Atomic Structure & The Periodic Table

Topic 1 - Atomic Structure & The Periodic Table

1. Electrons & Protons = Atomic Number Neutrons = Mass Number - Atomic Number

   • The number of protons in an atom determines what type of atom it is, so if all the atoms have the same number of protons, then the substance is an element.
     • Aluminium = 2,8,3 Argon = 2,8,8
       • Elements with similar properties form columns called groups. Therefore chlorine and bromine react in similar ways. The group number can tell you how many electrons there are in the outer shell.
       • Potassium forms 1+ ions as it's in the same group as sodium so will react in a similar way.

2. Na2CO3 = 6 Atoms (2 x Na) + (1 x C) + (3 x 0)

   • CaCl2 ~ Compound = Calcium Chloride Element = Calcium & Chlorine
     • Bromine would displace iodine in potassium iodide because bromine is more reactive the iodine.
   • Fe + Cl2 -> FeCl3 (BALANCED) 2Fe + 3Cl2 -> 2FeCl3
     • Water -> Hydrogen + Oxygen 2H2O -> 2H2 + O2 (Balanced)

3. You shouldn't use a pen to draw a line on the filter paper for paper chromatography because the ink will rise up the filter paper and will dissolve in the solvent.

   • Crystallisation - pour the solution into an evaporating dish and slowly heat the solution until crystals start to form or some of the solvent has evaporated. Leave the dish to cool until crystals are formed. Filter, and then dry the crystals using a desiccator/drying oven.
     • Propan 1 -ol = 97 C, Methanol = 65 C & Ethanol = 78 C. Which liquid will be collected in the second fraction of fractional distillation and why?
       • Ethanol. Ethanol has the second lowest boiling point and will be collected once all the methanol has been distilled off and the temperature increased.

4. In the plum pudding model, the atom is a ball of positive charge with electrons spread throughout it.

   • Rutherford devised an experiment where alpha particles were fired through gold foil. Most of the particles passed through the foil, but some were deflected by different angles, and some were even deflected backwards. Why does the disprove the plum pudding model?
     • If the plum pudding model was correct, you would expect most of the alpha particles to have passed through the foil or only to have been defelcted slightly. the actual deflections of the particles sguggest that atoms contain a small nucleus where the positive charge is concentrated.
   • Elements used to be classified by relative atomic mass.
     • Mendeleev left gaps in order to keep elements with similar properties in the same group. He switched the orger of elements based on their properties, even if their atomic masses were no longer in order.
       • As you go further down Group 1, the outer electron is further away from the nucleus. This means the attraction between the nucleus and the electron decreases so is more easily removed resulting in an increase in reactivity.
         • Halogens react by gaining electrons to make a full outer-shell. As you go further down Group 7, the outer electrons are further away so there is less attraction between them and the nucleus. This means electrons are harder to gain so they become less reactive.

5. Properties of metals = malleable, strong and good conductors of heat & electricity.

   • Xenon has a higher boiling boiling point than neon.
     • Noble Gases (higher boiling point as you go down):  Helium Neon Argon Krypton Xenon Radon
     • Argon is very unreactive because it has a full outer-shell so is electronically stable and does not readily lose or gain electrons.

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