Transition metals

• Transition metal: a metal the can form one or more stable ions with a partially filled d- subshell
• Transition metals can:

  • form complex ions
  • form coloured ions
  • are good catalysts
  • exist in variable oxidation states
• (Transition metal) Complex: central metal atom/ion surrounded by coordinately bonded ligands
• Possible shapes of complex ions:

  • octahedral (90)
  • tetrahedral (109.5)
  • square planar (90)
  • linear (180)
• Optical isomerism ( 3 bidentate ligands)

  • from of stereoisomerism
  • ions exists as two non-superimposable images
• Cis-trans

  • octahedral ( 4 x mono/ 2x different mono)
  • Square planar
• Solutions of (M)3+ are more acidic than solutions of (M)2+

  • M3+ have a higher charge density than M2+.... are more strongly polarising... they can attract electrons from the oxygen in water molecules more strongly...weakening the O-H bond.... more likely hydrogen will be released...more acidic
• Aqueous solution containing (CuCl4)2+ are yellow because:

  • Selective absorption of light
  • D electrons become excited/ absorb certain wavelengths of white light (=to energy gap)
  • The rest of the frequencies are transmitted/ reflected... these combine to make the complementary colour... colour observed
• The colour of a TM complex can be altered by a :

  • change in coordination number
  • change in oxidation state
  • change in (type of) ligand
• Autocatalyst: where the catalyst for a reaction is a reaction product
• the reaction between ethanedioate and potassium manganate is slow at first because:

  • like charge repulsion between Mno4- and C2O4-
  • This leads to a high activation energy
  • but as reaction progresses (formation of autocatalyst Mn2+) opposite charge attraction
• the concentration of aluminium sulfate cannot be determined by colorimetry as it is a colourless solution