transition metals

• coloured metals

  • Cr3+ = violet (or green)
  • Mn2+ = pink
  • Fe2+ = green
  • Fe3+ = yellow
  • Cu2+ = blue
• Cu2+ 2OH- -> pale blue (Cu(OH)2 )

  ammonia: +4NH3 -> [Cu(NH3)4 (H2O)2]2+ : royal blue

  sodium hydroxide: pale blue

  ammonia: royal blue
• Fe2+ + 2OH- -> Green (Fe(OH)2)
• Fe3+ + 3OH- -> Rust (Fe(OH)3)
• Mn2+ + 2OH- -> Brown (Mn(OH)2)
• Cr3+ + 3OH- -> Grey green (Cr(OH)3)

  excess sodium hydroxide: + 3OH- -> [Cr(OH)6] : dark green

  Ammonia: + 6NH3 -> [Cr(NH3)6]3- : purple

  sodium hydroxide: grey green

  excess sodium hydroxide: dark green

  Ammonia: purple