Transition metals

• Ligand substitution reaction


  When at least one ligand replaces another
• Incomplete ligand substitution reaction

  When not all ligands are replaced
• Bidentate ligands

  Some ligands can form two dative covalent bonds with the same transition metal ion
• Coordination number

  The number of dative covalent bonds formed with a transition metal ion
• Reaction where monodentate ligands are replaced by multidentate ligands

  The number of particles increases, so entropy increases
• Chelate effect

  When a multidentate ligand takes the place of monodentate ligands
• EDTA is a ligand that can form 6 dative covalent bonds with a metal ion, allowing it to absorb heavy metals like lead and prevent poisoning
• To make oxyhaemoglobin, a Fe^2+ ion forms: 4 bonds with a multidentate ligand (haem), 1 dative bond with a protein called globin (haemoglobin), and 1 unstable dative bond with O2 (or alternatively H2O or CO2)
• CO (carbon monoxide) forms a stable dative covalent bond with haemoglobin, permanently preventing it from functioning if haemoglobin gets a CO ligand
• Characteristics of transition metals

  • Complex formation
  • Formation of coloured ions
  • Variable oxidation state
  • Catalytic activity
• Coloured ions

  Formation of coloured ions occurs when there is room for an electron in one orbital to be excited into another orbital and the difference between their energy levels corresponds to a frequency of visible light
• Substance absorbs visible light

  Substance is seen as the complementary colour of the absorbed frequency
• Solutions containing transition metal ions are colourful if their transition metal ion has a partially filled d-subshell
• Solutions containing transition metal ions with empty or full d subshell are not colourful
• Ligand

  A molecule or ion with a lone pair, which forms a dative covalent bond with a transition metal ion
• Coordination number

  The number of dative covalent bonds to the metal ion
• Possible shapes of complexes:

  • Square planar (rarely)
  • Tetrahedral
  • Linear
  • octahedral
• What is the chelate effect?

  Multidentate ligands will replace monodentate as entropy increases whilst enthalpy stays roughly the same
• what are the conditions for a transition metal to emit a colour?

  incomplete d orbitals
• What is a catalyst?

  A substance that:

  Increases rate of reaction

  Without being used up

  lowers activation energy
• Homogeneous catalyst: same state as reactants
• Heterogeneous catalyst: different state than reactants
• Reasons to use a support medium

  • Increase surface area of active sites
  • reduce cost
• What kind of catalysts provide an active site for reactions?

  heterogeneous catalysts
• Ways to increase surface area?

  Turn the solid into a powder

  apply it as a coating to a support medium
• What is the contact process used for?

  To convert SO2 into SO3
• What catalyst and type is used in the contact process?

  V2O5

  Heterogeneous catalyst
• What is meant by catalyst poisoning?

  occurs when impurities bind onto a catalyst's binding sites and prevent it from functioning
• when a catalyst reforms itself at the end of the reaction we say it has been:

  Regenerated
• when a reaction produces its own catalyst we say its undergone autocatalysis
• What is an autocatalyst?

  a catalyst which is one of the products of the reaction it is catalysing
• Reasons why the Rate of reaction curve can appear as an s with Manganese oxide and ethandioate ions?

  1. Ions are negative and repel
  2. eventually positive Mn ions form which is the autocatalysts
  3. rate of reaction drastically increase
  4. rate of reaction decreases as concentration of reactants decreases
• 3 ways a transition metal complex can be altered to change its colour?


  1. Changing coordination number
  2. oxidation state of metal ion
  3. type of ligands
• shape and colour of [Cu(Cl)4]2-?

  tetrahedral, Dark blue
• What is a transition metal?

  A metal that has partially filled d orbitals in its atom or ion form
• why is titrating with KMnO4 not require an indicator

  KMnO4 is self indicating with Mn(VII) In the form of MnO4- being a dark purple colour and Mn2+ ions being pink (very light)
• What catalyst and type is used in the contact process?


  Catalyst: Vanadium(V) oxide, V2O5 Type: Heterogeneous
• Write the equations that occur during the contact process

  and the initial conditions

  SO2 + V2O5 -> SO3 + V2O4

  (V goes from +5 to +4)

  V2O4 +1/2O2 -> V2O5

  S burnt to produce SO2, mixed with oxygen and run over the heterogeneous catalyst where the above occurs
• What is catalyst poisoning?


  When impurities bind onto a catalyst's active sites and prevent it from functioning and reducing the number of available active sites, reducing efficacy.
• Bidentate ligands to know

   H2NCH2CH2NH2 and C2O42–