Chemistry paper 1

• What are the charges and masses of a proton, neutron and electron

  
• Why are atoms always neutral?
• Mass number


  Protons and neutrons
• Isotope


  An atom with the same number of protons but a different number of neutrons
• How do you calculate the relative atomic mass of an isotope

  
• Group number


  Number of electrons in the outer shell
• Period


  How many shells the atom has
• Distillation


  Used to separate liquids with different boiling points
• Transition metals


  • Can be used as catalysts, Form coloured compounds so can be used in pottery, Hard – High mp and bp, Low reactivity with water/oxygen, Varying oxidation states
• Group one metals


  • Soft – low mp/bp, Low density – float on water, Form white compounds, React vigorously with water (form alkali metals), Stored under oil (react with oxygen in air), Form 1+ ions (in group 1), React with non-metals to form ionic compounds
• Location of metals and non-metals in the periodic table

  • Metals on the left, non-metals on the right, Group 1 – Alkali Metals, Group 7 – Halogens, Group 8 – Noble Gases (don't react)

  
• How to work out the number of protons, neutrons and electrons in an atom


  Protons = atomic number, Electrons = same as protons, Neutrons = Mass number – atomic number

  
• Uses of noble gases

  • Helium – Balloons, Neon – Signs, Argon – Light bulbs (stops oxygen combusting with hot filament)
• As you go down group 1, 7 or 8


  The mp/bp increases
• Electron configuration of oxygen
• Why reactivity increases down group 1

  Increase number of shells, More shielding, Less attraction between positive nucleus and negative outer electron, Electron is lost more easily

  
• How do all group 7 atoms exist
• Development of the atom model

  • Democritus (one solid mass) → Dalton (could combine to make compounds) → JJ Thompson (Plum Pudding) → Rutherford (Gold Foil) → Bohr (electron) → Chadwick (neutrons – isotopes)

  
• What did Rutherford's experiment determine
• Ionic bond


  Formed between metals and non-metals, Electrons are transferred
• Charges of metals and non-metals in ionic bonds

  Metals become positive (lose electrons), Non Metals become Negative (gain electrons)
• What sticks an ionic bond together

  Electrostatic attraction between positive metal and negative non-metal
• Covalent bond


  Formed between two non metals, Electrons are shared
• Metallic bond


  Formed between metals, Electrostatic attraction between positive metal ions and sea of delocalised electrons
• Why do ionic compounds have high melting and boiling points
• Why do simple covalent compounds have low melting and boiling points
• State of simple molecular compounds at room temp

  GAS OR LIQUID (weak intermolecular forces)
• Why are metals malleable

  Arranged in layers so the layers can slide over each other
• Why are alloys harder than pure metals

  Alloys are mixture of metals/non-metals. Impurities distort layers so they can no longer slide over each other. Also cheaper due to impurities
• Why can metals conduct heat

  Atoms vibrate, Delocalised electrons can move, Transfer heat energy to atoms
• Why can metals conduct electricity

  Sea of delocalised electrons free to move, Can carry a charge

  
• Why is diamond very hard and cannot conduct electricity

  Giant lattice – each carbon has 4 strong covalent bonds to other carbons, Takes a lot of energy to break bonds, No free electrons to conduct and carry charge
• Uses of diamond


  • Jewellery – Shiny, End of drills – very hard
• Why is graphite soft and can conduct electricity

  Arranged in hexagonal layers with weak intermolecular forces between layers, Each C has three bonds only, Leaves free electrons which are delocalised and free to move between layers and carry a charge

  
• Fullerene


  Cage/ball of carbon atoms, Can be used for drug delivery (hollow), As lubricants (spherical can slide), As Catalysts (small), Sports equipment (very lightweight)
• Nanotubes


  Very strong but quite light, Can be used as reinforcement in sports equipment
• Why are nanoparticles useful as catalysts

  Very small, High Surface area to volume ratio
• Why do polymers have very high melting points and boiling points

  Very large molecules, Lots of intermolecular forces between molecules which take a lot of energy to break
• Why would thermosoftening polymers be no good for take away cans
• Why are polymers harder and cheaper than pure metals

  Distortions – layers cannot slide (harder), Impurities – Cheaper