transition metals

• What defines a transition metal?

  Incomplete d subshell in atoms or ions
• What is a ligand?

  particle with lone pair that bonds to metals by a co-ordinate bond
• What is a complex?

  Metal ion with co-ordinately bonded ligands
• What is the coordination number?

  Number of co-ordinate bonds to central metal atom
• What is a Lewis base?

  Lone pair donor
• What is a Lewis acid?

  Lone pair acceptor
• Why do transition metals have variable oxidation states?

  They can form more than one positive ion
• How do ligands interact with transition metals?

  They bond by donating electron pairs
• What is the significance of coordination number in complexes?

  It determines the shape of the complex
• What are the shapes and bond angles of complexes based on coordination number?

  • Coordination number 2: Linear, 180
  • Coordination number 4: Square planar, 90 or Tetrahedral, 109.5
  • Coordination number 6: Octahedral, 90
• What is a monodentate ligand?

  Forms one dative bond to metal ion
• What is a bidentate ligand?

  Forms two dative bonds to metal ion
• What is a multidentate ligand?

  Forms more than two dative bonds
• What happens during ligand substitution by similar sized ligands?

  No change in coordination number occurs
• What happens during ligand substitution by bigger or smaller ligands?

  Coordination number changes
• What is the chelate effect?

  Replacement of monodentate ligands with bidentate or multidentate ligands
• Why do coloured ions absorb light?

  light is absorbed to excite electrons to higher energy levels
• What determines the color of a transition metal complex?

  Size of energy gap and light absorbed
• What factors affect the color of transition metal complexes?

  Identity of metal, oxidation state, ligands
• What is UV spectroscopy used for?

  Measures frequency of light absorbed by complexes
• How does colorimetry determine concentration?

  By measuring absorption and using calibration curve
• What are common oxidation states of Iron?

  +2, +3, +6
• What are common oxidation states of Manganese?

  +2, +4, +6, +7
• What are common oxidation states of Copper?

  +1, +2
• What are the uses of transition metals in testing and catalysis?

  • Testing for aldehydes: Tollens reagent, Fehling’s solution
  • Testing for alcohols: Acidified potassium dichromate
  • Redox titrations: Acidified potassium manganate (KMnO₄)
  • Catalysis: Transition metals change oxidation state
• How does pH affect the oxidation state of transition metals?

  Alkaline conditions favour oxidation, acidic favour reduction
• conditions for reducing V5+ to V2+

  acidic conditions

  HCl or sulfuric acid
• What color changes occur during the reduction of vanadium?

  Yellow → blue → green → violet
• What is the strong oxidizing agent in redox titrations?

  Potassium manganate (MnO₄⁻)
• What is the endpoint in a redox titration with MnO₄⁻?

  Purple MnO₄⁻ turns colourless to Mn²⁺
• What is a catalyst?

  substance that increases the rate of a chemical reaction, but is not used up

  provides alternative route with lower activation energy
• What is heterogeneous catalysis?

  Catalyst in different phase from reactants
• What is catalyst poisoning?

  Other substances block active sites on catalyst
• What is the contact process in catalysis?

  Conversion of SO2 to SO3 using vanadium oxide
• What is homogeneous catalysis?

  Catalyst in same phase as reactants
• How do transition metals act as homogeneous catalysts?

  Variable oxidation states allow catalytic action
• What is autocatalysis?

  Reactions produce their own catalysts from products
• How do ligands influence the properties of transition metal complexes?

  They determine colour, stability, and reactivity
• more positive electrode potential = easier to reduce
• easier to reduce transition metals in acidic conditions