Chemistry, 9: The periodic table

• Elements are in order of increasing proton numbers
• The rows are called periods
• The columns are called groups
• Group number corresponds to number of electrons on the outer shell
• For Group I to Group IV, reactivity decreases
• For group IV to group VII, reactivity increases
• Group I are the alkali metals
• Group II are alkali Earth metals
• Group VII are halogens
• Group VIII are noble gases
• From top to bottom, metals become more reactive

  This is because as the metal atom gets bigger, the electrons gets further away from the nucleus and can be removed more easily to form positive ions.
• From top to bottom, non-metals become less reactive

  This is because the smaller the atom, the nearer the outer shell is to the nucleus and it is easier to attract other atoms to get a full shell.
• Group VIII(0) elements are noble gases that are very un-reactive as they have a full outer shell
• Group I metals reacts with air and water

  This produces alkaline solution with water
• Group I elements only have one electron in the outer shell which is easily given away when reacts with a non-metal
• The more electrons a metal atom has, the more energy is needed to start the reaction
• What are the properties of Group I metals?

  Soft to cut

  Shiny when cut, oxidizes in air quickly

  Low melting point, decreases as you go down

  Low density, increases as you go down

  Reacts easily with water, air, and elements like chlorine

  Stored in oil to prevent reaction with air and water
• What happens when Group I metals reacts with air/oxygen?


  Metal burns easily and their compound flame
• What happens when Group I metals react with water?


  Reacts vigorously, floats on the surface and moves around rapidly

  Resulting solution is alkaline

  With more reactive metals, hydrogen gas is produced
• What happens when Group I metal reacts with chlorine?


  Reacts easily

  Burns in chlorine to form white solid
• Compounds of Group I metals are often colourless or white solids

  They always have ionic bonding and most are soluble in water
• What are some compounds of the Group I metals?

  • Lithium carbonate, hardener in glass and ceramics
  • Lithium hydroxide, removes CO2 in air-conditioning
  • Sodium chloride, table salt
  • Sodium carbonate, water softener
  • Sodium hydroxide, used in paper manufacture
  • Monosodium glutamate, flavor enhancer
  • Sodium sulfate, preservative
  • Potassium nitrate, fertiliser that is also used in explosives
• Group VII elements are non-metals known as halogens

  They are highly reactive
• Group VII are salt makers, as they react with metals to make salts
• Group VII metals have 7 electrons in their outermost electron shell

  Only needs 1 more electron for a full outer shell, therefore highly reactive
• Group VII elements forms negative ions when it reacts with metals
• What are the properties of Group VII elements?


  Diatomic molecules

  Reacts with metals to form salts

  Undergoes displacement reactions

  Fluorine, pale-yellow gas

  Chlorine, pale-green gas

  Bromine, red-brown liquid

  Iodine, black shiny solid
• What happens when Group VII elements reacts with water?


  Dissolves in water, forming solutions that behaves like bleach
• What happens when Group VII elements reacts with metals?

  Halogens form salts with all metals
• What happens when Group VII elements undergoes displacement?

  A more reactive halogen will displace a less reactive halogen from a solution of a salt

  E.g. Chlorine displaces iodine from sodium iodide solution, colourless sodium iodide turns brown when chlorine is added
• Displacement reactions between halogens and solutions of halide ions are redox ions
• What are the uses of halogens?


  Fluoride, toothpastes

  Fluorine compounds, making plastic

  Chlorofluorocarbon, propellant in aerosol and refrigerant

  Chlorine, purifies water

  Chlorine compounds, household bleach

  Hydrochloric acid, widely used in industry

  Bromine compounds, making pesticides

  Silver bromide, light-sensitive film coating on photographic film

  Iodine solution, antiseptic
• Transition metals have >1 electron in their outer shell and are good catalysts
• Transition metals are less reactive than group I and II elements
• Transition metals have a higher melting point and high density
• Transition metals react slower with water and oxygen

  It can be used as construction metals
• Compounds of transition metals are often coloured
• Copper tends to be blue or green

  Iron tends to be green or brown
• When sodium hydroxide is added to solution of metal compound, a ppt of the metal hydroxide is formed

  The colour of the ppt can identify the metal
• What metal is present when metal hydroxide is blue?


  Copper (II) Cu2+