Chemistry

• Elements are a single type of atom
• An atom is a very, very small thing
• The word atom is actually Greek for uncuttable
• The periodic table lists all the elements which are known to exist
• Compound


  Two or more elements that are chemically bonded together
• Atom structure


  Electrons on the shells around the outside, protons in the middle, and neutrons in the middle
• Protons


  In the nucleus, mass of 1, charge of plus 1
• Neutrons


  In the nucleus, mass of 1, charge of zero
• Electrons


  In the outer shells, mass 1/2000, charge of minus 1
• Atomic number


  Number of protons and electrons in an atom
• Mass number


  Number of protons plus the number of neutrons
• Balancing a chemical equation

  Write the reactants and products, count the atoms, adjust coefficients to balance
• Important chemical formulas to learn

  • Carbon dioxide CO2
  • Water H2O
  • Oxygen gas O2
  • Hydrogen gas H2
  • Nitrogen gas N2
  • Ammonia NH3
  • Hydrochloric acid HCl
  • Sulfuric acid H2SO4
• Element


  Pure substance made of a single type of atom
• Compound


  Two or more different elements chemically bonded together
• Mixture


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

  • Distillation
  • Evaporation
  • Filtration
  • Fractional distillation
• The plum pudding model of the atom was disproven by the Rutherford-Marsden experiment
• 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


  Draw the shells, fill the electrons based on group and period
• Ions


  Atoms that have lost or gained electrons, resulting in a positive or negative charge
• Periodic table groups


  • Group 1 alkali metals
  • Group 2 alkaline earth metals
  • Group 6 chalcogens
  • Group 7 halogens
  • Group 8 noble gases
  • Transition metals
• Mendeleev's periodic table had gaps for undiscovered elements, which were later filled
• Noble gases


  Have a full outer shell, are unreactive
• Halogens


  Highly reactive nonmetals that form diatomic molecules and want to gain 1 electron
• More reactive element


  Can displace a less reactive element from a compound
• Halogens are 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 because chlorine is higher than bromine on the periodic table, so it's 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 are used in fireworks
• Alkali metals need to be kept in oil so they don't react with oxygen or water in the air
• What happens when a metal reacts with oxygen


  Metal oxide is formed, which causes the metal to dull in appearance
• What happens when a metal reacts with water

  Metal hydroxide is formed, which is alkaline
• Reactions with alkali metals are very exothermic and release hydrogen gas
• Reactivity of elements


  Most reactive at the bottom of the periodic table, least reactive at the top