Periodic Table

• The Periodic Table is an arrangement of elements in the order of increasing proton number
• The position of an element in the Periodic Table is related to its proton number and electronic configuration
• Valence electrons of an element correspond to the last digit of their respective group number
• The number of electron shells corresponds to the period number
• Elements with the same amount of valence electrons have similar properties, and these properties remain the same down the group
• The metallic character increases down the group and decreases across a period.

  The non-metallic character decreases down the group and increases across a period.
• The number of valence electrons influences the metallic/non-metallic character of elements
• Group 1 (alkali metals): Lithium sodium and potassium are...

  • soft (can be cut easily)
  • low-density metals (density is below 1, which is that of water)
  • Very reactive (rapidly tarnish in air)
  • Have low melting and boiling points
  • Reactivity of Group 1 increases down the group
  • Melting and boiling points decrease down the group
• Group 17 (halogens) are...

  • Diatomic nonmetals
  • Nonmetals with low melting and boiling points
  • Coloured (fluorine; pale yellow, chlorine; yellow-green, bromine; red-brown, iodine; purple-black)
  • less-reactive down the group
  • able to displace less reactive halogens from their halide solutions
  • More intense in colour down the group
  • Increasing in melting and boiling points down the group
• Elements in Group 18 (noble gases) are...

  • monoatomic
  • chemically unreactive due to their stable octet EC
  • important in providing an inert environment
  • increasing in melting and boiling points down the group
• Transition metals have...

  • high melting and boiling points
  • high densities
  • variable oxidation states
  • ability to form coloured compounds
  • ability to be good catalysts for chemical reactions
• LITHIUM REACTION WITH WATER

  • Lithium floats and moves slowly across surface of the water
  • Effervescence is observed
  • Reacts quickly
  • 2Li (s) + 2H2O (l) -> 2LiOH (aq) + H2 (g)
• SODIUM REACTION WITH WATER

  • Sodium floats and darts quickly across surface of the water
  • Mild effervescence observed
  • Reacts violently
  • 2Na (s) + 2H2O (l) -> 2NaOH + H2
• POTASSIUM REACTION WITH WATER

  • Potassium floats very quickly across the surface of the water
  • It ignites with a lilac flame
  • Vigorous effervescence observed
  • Reacts explosively
  • 2K (s) + 2H2O (l) -> 2KOH (aq) + H2 (g)