Chemistry

• Nucleus


  Always positive
• Electron


  Always negatively charged
• Isotopes


  They have the same amount of protons but different number of neutrons
• Relative atomic mass


  Sum of (isotope abundance x isotope mass) / Sum of abundance of all isotopes
• Compounds are 2 or more elements chemically bonded/joined
• Mixtures have no chemical bond and can be separated by physical means
• Ionic bonding


  Metal loses electron, non-metal gains electron, forming oppositely charged ions that are strongly bonded
• Covalent bonding


  Non-metals share electrons between them, forming molecules
• Diatomic molecules


  • Hydrogen
  • Nitrogen
  • Fluorine
  • Oxygen
  • Iodine
  • Chlorine
  • Bromine
• Balanced chemical equation


  1. Write reactants

  2. Identify products

  3. Balance equation
• Chromatography


  • Draw pencil line at bottom of paper
  • Place ink dot on line
  • Place paper in solvent, ensure ink doesn't touch
  • Cover to prevent evaporation
• Physical separation techniques


  • Filtration
  • Evaporation
  • Crystallisation
  • Simple distillation
  • Fractional distillation
• Physical separation techniques do not work for compounds, only mixtures
• Filtration


  Separates insoluble solids from liquids, for purification
• Evaporation


  Separates soluble solids from solutions
• Crystallisation


  Separates soluble solids from solutions by evaporation and cooling
• Simple distillation


  Separates solutions by heating to boiling point, evaporating, and condensing
• Fractional distillation


  Separates mixtures with similar boiling points using a fractionating column
• History of the atom

  • Dalton - atom is solid sphere
  • Thomson - plum pudding model
  • Rutherford - alpha particle experiment
  • Bohr - recent model
• Electronic structure


  Configuration of energy levels (shells)
• Periodic table


  • Originally sorted by mass, now by atomic number
  • Created by Dmitri Mendeleev
• Group 1 elements (alkali metals)


  • Very reactive
  • Soft and low density
  • First 3 denser than water
  • Have 1 electron in outer shell
• Trends in group 1 elements

  • Increasing reactivity
  • Outer electrons more easily lost
  • Decreasing melting/boiling point
  • Increasing relative atomic mass
  • Decreasing attraction between nucleus and electrons
• Alkali metals form ionic compounds with non-metals


  They easily lose their one outer electron to form a full outer shell
• Reaction of alkali metals with water

  Produce hydrogen gas and metal hydroxide
• Group 7 elements (halogens)


  • Non-metals with coloured vapours
  • Exist as diatomic molecules
  • Decreasing reactivity down group
• Trends in group 7 elements

  • Decreasing melting/boiling points
  • Harder to gain electrons
  • Increasing relative atomic mass
• Group 8 elements (noble gases)

  • Have full outer shells so are very unreactive
  • Increasing boiling points with increasing number of electrons
• Metals


  • Malleable, strong, good conductors of heat and electricity, high melting/boiling points
• Non-metals


  • Dull looking, brittle, poor conductors of electricity, low density
• Transition metals


  • Typical metal properties
  • Form more than one ion
  • Compounds are usually colourful
  • Good catalysts
• Chemical properties of groups

  • Group 1 - form ionic compounds, react with water
  • Group 7 - form molecular compounds, toxic gases
  • Group 8 - unreactive, don't form compounds