Chemistry

• Element


  A pure substance that cannot be broken down into simpler substances by chemical means
• Pure substance


  • Has a fixed melting and boiling point
  • A mixture may melt or boil over a range of temperatures
• Atom


  The smallest particle of an element that retains its chemical properties
• Atom structure


  • Positions, relative masses and relative charges of sub-atomic particles
• Atomic number


  The number of protons in the nucleus of an atom
• Periodic Table


  • Elements are arranged in order of atomic number
  • Elements are arranged in groups and periods
• Deducing electronic configurations


  1. Use position in Periodic Table

  2. For first 20 elements
• Classifying elements


  • Use electrical conductivity
  • Use acid-base character of oxides
• Elements in the same group of the Periodic Table have similar chemical properties
• Noble gases (Group 0) do not readily react
• Group 1 (alkali metals)


  • Lithium
  • Sodium
  • Potassium
• Alkali metals


  • Similarities in reactions with water provide evidence for family
  • Differences in reactions with air and water provide evidence for trend in reactivity
• Knowing trends in Group 1

  Can predict properties of other alkali metals
• Electronic configurations


  Explain trend in reactivity in Group 1
• Group 7 (halogens)


  • Chlorine
  • Bromine
  • Iodine
• Halogens


  • Colours
  • Physical states (at room temperature)
  • Trends in physical properties
• Knowing trends in Group 7

  Can predict properties of other halogens
• Halogens and halides


  • Displacement reactions provide evidence for trend in reactivity
• Electronic configurations


  Explain trend in reactivity in Group 7
• Ion


  Atom or group of atoms with an electric charge, formed by loss or gain of electrons
• Ions


  • Metals in Groups 1, 2 and 3
  • Non-metals in Groups 5, 6 and 7
  • Ag+, Cu2+, Fe2+, Fe3+, Pb2+, Zn2+
  • Hydrogen (H+), hydroxide (OH-), ammonium (NH4+), carbonate (CO32-), nitrate (NO3-), sulfate (SO42-)
• Writing ionic compound formulae

  1. Use charges of ions

  2. Combine to form neutral compounds
• Drawing dot-and-cross diagrams


  1. Show formation of ionic compounds by electron transfer

  2. Limit to combinations of elements from Groups 1, 2, 3 and 5, 6, 7

  3. Only show outer electrons
• Ionic bonding


  Electrostatic attractions between oppositely charged ions
• Ionic compounds


  • Have high melting and boiling points
  • Do not conduct electricity when solid
  • Conduct electricity when molten and in aqueous solution
• Covalent bond


  A bond formed between atoms by the sharing of a pair of electrons
• Covalent bonds


  • Formed by electrostatic attractions
  • Can be represented using dot-and-cross diagrams
• Diatomic molecules represented by dot-and-cross diagrams

  • Hydrogen
  • Oxygen
  • Nitrogen
  • Halogens
  • Hydrogen halides
• Inorganic molecules represented by dot-and-cross diagrams

  • Water
  • Ammonia
  • Carbon dioxide
• Organic molecules with up to two carbon atoms represented by dot-and-cross diagrams

  • Methane
  • Ethane
  • Ethene
  • Halogen-containing
• Intermolecular forces of attraction

  Forces between molecules
• Substances with simple molecular structures

  Are gases, liquids, or solids with low melting and boiling points
• Melting and boiling points of substances with simple molecular structures


  Increase with increasing relative molecular mass
• Substances with giant covalent structures


  Are solids with high melting and boiling points
• Diamond, graphite, and C60 fullerene

  • Their structures influence their physical properties, including electrical conductivity and hardness
• Covalent compounds do not usually conduct electricity
• States of matter


  Arrangement, movement, and energy of particles
• Interconversions between the three states of matter

  1. Names of the interconversions

  2. How they are achieved

  3. Changes in arrangement, movement, and energy of the particles
• Experiments involving the dilution of coloured solutions and diffusion of gases can be explained by the three states of matter
• The approximate percentages by volume of the four most abundant gases in dry air