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'
• There are still many elements yet to be discovered
• 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
• Balancing a chemical equation

  1. List the reactants and products

  2. Count the number of each element

  3. Adjust the coefficients to balance the equation
• 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


  • 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 disproved the plum pudding model and led to the development of the nuclear model</b>
• Rutherford discovered the nucleus, Chadwick discovered neutrons, and Bohr developed the current atomic model
• Groups


  Go down the periodic table, indicate the number of electrons in the outer shell
• Periods


  Go across the periodic table, indicate the number of electron shells
• Determining electronic configuration


  1. Identify the group and period

  2. Draw the shells with the correct number of electrons
• Sodium ion


  Has 11 protons and 10 electrons, giving it an overall positive charge
• Periodic table groups


  • Group 1 (alkali metals)
  • Group 2 (alkaline earth metals)
  • Group 6 (halogens)
  • Group 7 (halogens)
  • Group 8 (noble gases)
  • Transition metals
• Newlands' early periodic table had flaws as he arranged by mass without leaving gaps
• Mendeleev's periodic table was accepted as he arranged by properties and left gaps for undiscovered elements
• Noble gases


  Have a full outer shell and are very unreactive
• Halogens


  Highly reactive nonmetals that form diatomic molecules and want to gain 1 electron
• 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 colors which can be used in fireworks
• Alkali metals need to be kept in oil to prevent reaction with oxygen or water in the air
• Reaction of metal with oxygen


  1. Metal + oxygen → metal oxide

  2. Shiny metal dulls due to formation of metal oxide
• Reaction of metal with water

  1. Metal + water → metal hydroxide

  2. Produces hydrogen gas, is exothermic and alkaline