Chapter 24 TRANSITION ELEMENTS

• What are d-block elements by definition?

  The d-block elements are elements in groups 3 through 12 in which the highest electron energy subshell is a d-subshell
• What are the characteristics of d-block elements?

  Metallic so

  • high mp, bp and denisty
  • shiny appearance
  • conduct electricity & heat
• Why does electron configuration of Chromium and Copper differ?

  Half-filled and fully-filled subshells are more stable therefore they form 3d5, 4s1 and 3d10, 4s1 configuration
• What are transition elements by definition?

  D-block elements that form at least one ion with a partially filled d-orbital
• Which 2 elements are d-block elements but not transition elements and why?

  Scandium and Zinc. They do not have partially filled d orbitals in their common oxidation states
• Which ions do Scandium and Zinc only form?

  Sc3+ and Zn2+
• What are the properties of transition metals?

  • form compounds which the transition element has different oxidation states - e.g. Fe2+ & Fe3+
  • form coloured compounds
  • elements and compounds act as catalysts - e.g. Fe in Haber Process or Pt/Pd in catalytic converters
  • form complexes (ligands form coordinate bonds)
• What colour is Cu2+?

  Blue
• What colour is MnO4-?

  Purple
• What colour is Fe3+?

  Yellow
• What are some uses of transition elements?

  • making coins
  • construction
  • tools & electrical cables/water pipes
• What is a ligand?

  A ligand is a molecule or ion that has one or more lone pairs of electrons which can be donated in a coordinate bond or dative covalent bond to a central cation
• What must ligands be to form complex ions?

  Neutral molecules or anions because same charges repel
• What catalyst is involved in the Haber process?

  Iron catalyst for manufacturing ammonia
• What catalyst is involved in the Contact process?

  Vanadium pentoxide for manufacturing sulphur trioxide
• What is coordination number?

  Coordination number indicates number of coordinate bonds attached to a central metal ion
• What is a monodentate ligand and give examples?

  Monodentate ligands donate one lone pair of electrons to a central metal ion.

  Examples: $H_2O:,\ :NH_3,\ :OH^-$
• What is a bidentate ligand and give examples?

  A ligand that donates 2 lone pairs of electrons to a central metal ion.

  Examples: $:NH_2CH_2CH_2H_2N:$, :OOCCOO:
• What shape do complex ions with 6 coordinate bonds form, what bond angle and give examples?

  Octahedral complexes, bond angle 90 degrees

  Examples: $\left[Mn\left(H_2O\right)\right]^{^+}$
• What shape do complex ions with 6 coordinate bonds form, what bond angle and give examples?


  Octahedral complexes, bond angle 90 degrees

  Examples: $\left[Mn\left(H_2O\right)_6\right]^{2+}$ and $\left[Co\left(H_2NCH_2CH_2NH_2\right)_3\right]^{3+}$
• What shapes do complex ions with 4 coordinate bonds form, what bond angle and give examples?

  Tetrahedral complexes, bond angle 109.5 degrees

  Planar complexes, bond angle 90 degrees

  Examples: $\left[Pt\left(NH_3\right)_4\right]^{2+}$and $\left[CoCl_4\right]^{2-}$
• What types of stereoisomerism are shown in complexes?

  Cis-trans isomerism in square planar complexes

  Octahedral complexes also demonstrate cis-trans isomerism with monodentate and bidentate ligands
• When does optical isomerism occur in complex ions?

  It only occurs in octahedral complexes which contain two or more bidentate ligands
• What are optical isomers?

  They are non-superimposable mirror images of each other (enantiomers)
• How is cis-platin used as an anti-cancer drug?

  Cis-platin forms a platinum complex inside cells which binds to DNA, preventing replication and eventually leads to apoptosis. It however has many unpleasant side effects
• What is a ligand substitution reaction?

  One in which one ligand in a complex ion is replaced by another ligand.
• What colour is $\left[Cu\left(H_2O\right)_6\right]^{2+}$and when is it formed?


  Pale blue solution when Copper (II) sulphate dissolves in water
• What forms when $\left[Cu\left(H_2O\right)_6\right]^{2+}$reacts with excess $NH_3\left(aq\right)$?


  A dark blue solution of the complex ion, $\left[Cu\left(NH_3\right)_4\left(H_2O\right)_2\right]^{2+}$
• What forms when $\left[Cu\left(H_2O_6\right)\right]^{2+}$ reacts with concentrated HCl?


  In excess, a yellow solution forms: $\left[CuCl_4\right]^{2-}$

  If concentrated HCl is added drop-wise, a green intermediate forms as the result of the blue and yellow solution mixing
• What colour is $\left[Cr\left(H_2O\right)_6\right]^{3+}$?


  A pale purple solution
• What colour is $\left[Cr\left(H_2O\right)_5SO_4\right]^+$?


  A green solution
• What colour is $\left[Cr\left(NH_3\right)_6\right]^{3+}$?


  A purple solution
• What is the biochemical importance of iron in haemoglobin?

  Haemoglobin contains iron which contains 4 protein chains held together by weak intermolecular forces
• How does haemoglobin transport oxygen and carbon dioxide?

  Oxygen binds to Fe2+ central metal ion by formation of coordinate bond in the lungs which releases oxygen to body cells as they have a lower concentration of O2. Carbon dioxide binds to Fe2+ to be carried back to the lungs and released in the lungs
• How does carbon monoxide affect the body?

  It binds to haemoglobin and the bond is so strong that the process is irreversible that oxygen transport is prevented
• What is observed when Cu2+ ions react with NaOh(aq)?

  Blue solution -> Blue precipitate of Cu(II) hydroxide

  Equation: Cu2+ + 2OH- -> Cu(OH)2
• What is observed when Fe2+ ions react with NaOH(aq)?

  Pale green solution -> green precipitate of Fe(II) hydroxide

  Equation: Fe2+ + 2OH- -> Fe(OH)2

  Insoluble in excess NaOH but turns to orange-brown precipitate of Fe3+
• What is observed when Fe3+ ions react with NaOH(aq)?

  Pale yellow solution -> orange-brown precipitate of Fe(III) hydroxide

  Equation: Fe3+ + 3OH- -> Fe(OH)3

  Insoluble in excess NaOH
• What is observed when Mn2+ ions react with NaOH(aq)?

  Pale pink solution -> light brown precipitate of Mn(II) hydroxide

  Equation: Mn2+ + 2OH- -> Mn(OH)2

  Insoluble in excess NaOH
• What is observed when Cr3+ ions react with NaOH(aq)?

  Violet solution -> grey-green precipitate of Cr(III) hydoxide

  Equation: Cr3+ + 3OH- -> Cr(OH)3

  Soluble in excess NaOH forming a dark green solution

  Equation: Cr(OH)3 + 3OH- -> [Cr(OH)6]3-