Periodic table

• Displacement of halogens:

  • Example 1: Chlorine + Sodium bromide -> Bromine + Sodium chloride
  • Chlorine displaces bromine from sodium bromide solution due to its higher reactivity
  • Word equation: Chlorine + sodium bromide -> Bromine + sodium chloride
  • Example 2: Bromine + Sodium chloride solution -> Red-brown solution
  • Explanation: Chlorine, being more reactive than bromine, displaces bromine from sodium bromide solution to form sodium chloride solution and aqueous bromine
• Group 18 (noble gases):

  • Have a completely filled outermost shell, leading to a stable electronic configuration
  • Chemically unreactive and exist as monatomic particles
• Halogens (Group 17):

  • Physical properties: exist as diatomic molecules, have low melting and boiling points, and are colored
  • Chemical properties: undergo displacement reactions with halide solutions, with a more reactive halogen displacing a less reactive halogen
• Appearance of halogens at room temperature:

  • Fluorine, F2: pale yellow gas
  • Chlorine, Cl2: pale green gas
  • Bromine, Br2: reddish/brown liquid
  • Iodine, I2: purple-black solid
  • Astatine, At2: purple-black solid
• Chemical properties of halogens:

  • React with cold water to form an alkali and hydrogen
  • Powerful reducing agents
  • Form soluble ionic compounds
  • Highly reactive, usually kept under oil
• Reactions of Group I metals with cold water:

  • Lithium: floats on water, no flame seen
  • Sodium: reacts very quickly, sodium melts into a silvery ball and rolls around the water surface, yellow flame seen
  • Potassium: reacts violently, potassium melts into a silvery ball and rolls around the water surface, lilac flame seen
• Transition elements:

  • Located between Group 2 and 13
  • Known as transition elements
  • Have properties of both metals and non-metals
• Alkali metals (Group 1):

  • Physical properties: soft, low boiling and melting points, low densities
  • Physical trend: melting and boiling points decrease down the group, densities increase
• The reactivity of the group 1 elements increases down the group.