Chemistry Paper 1

• The periodic table is a list of all the elements which are known to exist
• Element


  A single type of atom
• Atom


  A very small thing, the word atom is Greek for 'uncuttable'
• Compound


  Two or more elements that are chemically bonded together
• Structure of an atom

  • Electrons on the outer shells
  • Protons in the nucleus
  • Neutrons in the nucleus
• Protons


  Have a mass of 1 and a charge of +1
• Neutrons


  Have a mass of 1 and a charge of 0
• Electrons


  Have a mass of 1/2000 and a charge of -1
• Atomic number


  The number of protons and electrons in an atom
• Mass number


  The number of protons plus the number of neutrons
• Chemical formulas to learn

  • CO2 (carbon dioxide)
  • H2O (water)
  • O2 (oxygen gas)
  • H2 (hydrogen gas)
  • N2 (nitrogen gas)
  • NH3 (ammonia)
  • HCl (hydrochloric acid)
  • H2SO4 (sulfuric acid)
• Element


  A pure substance made of one type of atom
• Compound


  Two or more different elements chemically bonded together
• Mixture


  Lots of different substances, some chemically bonded, some not
• Separation techniques for mixtures

  • Distillation
  • Evaporation
  • Filtration
  • Fractional distillation
• Plum pudding model of the atom

  • A large cloud of positive charge with negative electrons dotted throughout
• Rutherford and Marsden's experiment

  1. Used an alpha particle gun

  2. Fired alpha particles at a thin gold foil

  3. Most went straight through, some deflected a little, some deflected a lot

  4. Suggested a small positive centre and a large negative outer region
• Rutherford discovered the nucleus and protons, Chadwick discovered neutrons, Bohr developed the current atomic model
• Groups in the periodic table

  Indicate the number of electrons in the outer shell
• Periods in the periodic table

  Indicate the number of electron shells
• Determining electronic configuration


  1. Identify the group and period

  2. Draw the correct number of shells

  3. Fill the shells with the correct number of electrons
• Metals


  Lose electrons, forming positive ions
• Non-metals


  Gain electrons, forming negative ions
• Groups in the periodic table

  • Group 1 (alkali metals)
  • Group 2 (alkaline earth metals)
  • Group 7 (halogens)
  • Group 8 (noble gases)
  • Transition metals
• Newlands' early periodic table was flawed as it didn't leave gaps for undiscovered elements
• Mendeleev's periodic table was accepted as it left gaps and accurately predicted properties of undiscovered elements
• Noble gases (group 8)

  • Have a full outer shell, so are unreactive
  • Have many uses like in balloons and neon lights
• Halogens (group 7)


  • Exist as diatomic molecules (Cl2, F2, Br2)
  • Highly reactive as they only need to gain 1 electron
  • Reactivity decreases down the group as boiling point increases
• A more reactive element


  Can displace a less reactive element in a compound
• Halogens are commonly used as sterilizing agents, e.g. chlorine in swimming pools
• Alkali metals react violently with water, producing colourful flames used in fireworks
• Bromine gas cannot displace chlorine out of sodium chloride, as chlorine is higher than bromine on the periodic table and more reactive
• Displacement reactions


  Reactions where one element displaces another element from a compound, forming a new compound
• Halogens are mostly used for sterilizing things
• Halogens


  Want to gain 1 electron, the most reactive ones are at the top of the periodic table where there is least shielding between the electron they want to gain and the nucleus
• Alkali metals react very violently with water, producing flames and different colours which are used in fireworks
• Alkali metals are soft, grey metals that need to be kept in oil to prevent reaction with oxygen or water
• Reaction of metal with oxygen


  1. Metal forms a metal oxide

  2. Metal oxide causes the metal to dull in appearance
• Reaction of metal with water

  1. Metal forms a metal hydroxide

  2. Reaction is exothermic and releases hydrogen gas
• Reactivity of elements


  • Most reactive at the bottom of the periodic table, least reactive at the top
  • Elements at the bottom have lower melting/boiling points