Periodic Table

• Lithium, sodium and potassium in Group I

  • A collection of relatively soft metals showing a trend in melting point, density and reaction with water
• Similar chemical properties of Group I elements

  They have the same number of outer shell electrons
• Identifying trends in Groups


  Going down a group means going up in number of electron shells, more electron shielding and so less attraction between the nucleus and outer shell electrons
• Melting points of Group I elements decrease going down the group
• Densities of Group I elements increase going down the group
• Reaction of Group I elements with water

  All react vigorously to create an alkaline solution and hydrogen
• Reactivity of Group I elements

  Increases going down the group
• It is easier to lose electrons going down Group I due to the increase in electron shells and electron shielding
• Halogens (chlorine, bromine, iodine) in Group VII


  • A collection of diatomic non-metals showing a trend in colour and density
• Reactivity of halogens


  Decreases going down the group
• A more reactive halogen will displace halide ions of a less reactive halogen
• Displacement reactions of halogens

  • Chlorine displaces bromide and iodide ions
  • Bromine displaces iodide but not chloride ions
  • Iodine does not displace chloride or bromide ions
• Transition elements


  • Metals with high densities, high melting points and which form coloured compounds, often acting as catalysts
• Variable oxidation states of transition elements


  They can form ions with different charges, e.g. Cu+ or Cu2+
• Oxidation states of transition metals are often shown using Roman numerals, e.g. iron(II) = Fe2+ and iron(III) = Fe3+
• Change from metallic to non-metallic character across a period


  Elements change from metallic to non-metallic character going from left to right across a period
• Metallic properties


  • Shiny
  • Conductive
  • Dense
  • Malleable
• Elements on either side of the red line in the periodic table are known as metalloids, having both metallic and non-metallic properties
• Relationship between group number, number of outer shell electrons and metallic/non-metallic character


  Group number shows the number of electrons in the outer shell. Metals form positive ions by losing electrons, non-metals form negative ions by gaining electrons. Groups 1 and 2 are all metals, groups 7 and 8 are all non-metals, with a transition in between.