Transition metals

• What is the general property of transition metals related to their electron configuration?

  They have an incomplete d sub-level in atoms or ions.
• Why is zinc not considered a transition metal?

  Because it can only form a +2 ion with a complete d orbital.
• What are the characteristics of transition metals?

  • Complex formation
  • Formation of coloured ions
  • Variable oxidation states
  • Catalytic activity
• What is a complex in chemistry?

  A complex is a central metal ion surrounded by ligands.
• What is a ligand?

  A ligand is an atom, ion, or molecule that can donate a lone electron pair.
• What is co-ordinate bonding?

  Co-ordinate bonding is when the shared pair of electrons in a covalent bond comes from only one of the bonding atoms.
• What is the co-ordination number?

  The co-ordination number is the number of co-ordinate bonds formed to a central metal ion.
• What are the types of ligands based on their bonding capabilities?

  • Monodentate: forms one coordinate bond (e.g., H2O, NH3, Cl-)
  • Bidentate: forms two coordinate bonds (e.g., NH2CH2CH2NH2, C2O42-)
  • Multidentate: forms multiple coordinate bonds (e.g., EDTA4-)
• What happens during substitution reactions involving ligands?

  Ligands can be exchanged without changing the co-ordination number.
• What is the result of adding concentrated chloride ions to an aqueous ion?

  It leads to a ligand substitution reaction and can change the co-ordination number.
• What is the chelate effect?

  The chelate effect is the increased stability of a complex when a monodentate ligand is replaced by a bidentate or multidentate ligand.
• How does the chelate effect relate to entropy?

  It leads to an increase in entropy due to more moles of products than reactants.
• What shapes do transition metal ions commonly form with ligands?

  • Octahedral complexes with small ligands (e.g., H2O, NH3)
  • Tetrahedral complexes with larger ligands (e.g., Cl-)
  • Square planar complexes (e.g., cisplatin)
  • Linear complexes (e.g., [Ag(NH3)2]+)
• What types of isomerism can complex ions exhibit?

  • Cis-trans isomerism
  • Optical isomerism
• What causes the formation of coloured ions in transition metals?

  Colour arises from electronic transitions between different d orbitals.
• What happens when a ligand or coordination number changes in a complex ion?

  It alters the energy split between the d-orbitals, changing the frequency of light absorbed.
• What is the equation that relates energy difference to frequency of light absorbed?

  ΔE = hv
• What is the speed of light?

  1. 00 × 10^8 m s^-1
• Why do compounds like Scandium and Zinc not exhibit colour?

  Because their d orbitals are either empty or fully filled, preventing electron transitions.
• What factors can cause colour changes in transition metal complexes?

  1. Change in oxidation state
  2. Change in coordination number
  3. Change in ligand
• What is the relationship between the absorbed light and the colour observed in transition metal complexes?

  • A portion of visible light is absorbed to promote d electrons to higher energy levels.
  • The light that is not absorbed gives the substance its observed colour.
• What is the significance of the equations ΔE = hv and ΔE = hc/λ?

  • They relate the energy difference between split d orbitals to the frequency and wavelength of light absorbed.
• What is the role of EDTA in environmental applications?

  • EDTA complexes are used to remove poisonous heavy metal ions from rivers.
  • It is also used in shampoos to remove calcium ions from hard water.
• What is the ion of Scandium in its ionic form?

  Sc$^{3+}$
• Why does Sc$^{3+}$ not have d electrons to transfer?


  Because it has lost all its d electrons.
• What is the electron configuration of Zn$^{2+}$ and Cu$^{+}$ ions?


  Both have a full d shell, e.g., 3d$^{10}$.
• What happens to the energy transfer in Zn$^{2+}$ and Cu$^{+}$ ions?


  There is no energy transfer equal to that of visible light.
• In the reaction [Co(H$_{2}O$)$_{6}$]$^{2+}$ + 6 NH$_{3}$ → [Co(NH$_{3}$)$_{6}$]$^{2+}$ + 6 H$_{2}O$, what is changing?


  Both ligand and coordination number are changing.
• How does color arise in transition metal complexes?

  It arises from the energy difference between split d orbitals.
• If a solution appears blue, what color light does it absorb?

  It absorbs orange light.
• What is the energy difference $\Delta E$ for a blue solution that absorbs orange light with a frequency of $5 \times 10^{14} \text{ s}^{-1}$?


  $\Delta E =$$3.32 \times 10^{-19} \text{ J}$
• What is the purpose of using spectrometry in colored ion solutions?


  To determine the concentration of colored ions.
• What is the method for determining the concentration of colored ions using spectrometry?

  1. Add an appropriate ligand to intensify color.
  2. Make up solutions of known concentration.
  3. Measure absorption or transmission.
  4. Plot graph of absorption vs concentration.
  5. Measure absorption of unknown and compare.
• What happens when visible light of increasing frequency passes through a colored complex ion?


  Some of the light is absorbed.
• How does the amount of light absorbed relate to the concentration of the absorbing species?

  The amount of light absorbed is proportional to the concentration.
• Why are some complexes pale in color and do not absorb light strongly?

  They require a suitable ligand to intensify the color.
• What is the role of a colored filter in a spectrometer?

  To allow wavelengths of light that are most strongly absorbed to pass through.
• What is a characteristic of transition elements regarding oxidation states?

  They show variable oxidation states.
• What are the general trends in oxidation states of transition metals?

  • Relative stability of +2 state increases across the period.
  • Compounds with high oxidation states tend to be oxidizing agents (e.g., MnO$_{4}^{-}$).
  • Compounds with low oxidation states are often reducing agents (e.g., V$^{2+}$ & Fe$^{2+}$).
• What is the significance of the redox titration between Fe$^{2+}$ and MnO$_{4}^{-}$?


  It is self-indicating due to the significant color change.