3.2.5
Transition
Metals
Section 3.2.5 covers the general properties of the transition metals from titanium to copper (3.2.5.1); ligand substitution, bidentate and multidentate ligands, haem and the chelate effect (3.2.5.2); the shapes of complex ions with cis–trans and optical isomerism, cisplatin and the linear [Ag(NH₃)₂]⁺ ion (3.2.5.3); the formation of coloured ions, ΔE = hν = hc/λ and colorimetry (3.2.5.4); variable oxidation states, the reduction of vanadate(V) by zinc, Tollens’ reagent and redox titrations with manganate(VII) (3.2.5.5); and heterogeneous and homogeneous catalysts, including autocatalysis (3.2.5.6).
Revision Notes
9 revision notes, in the order the specification teaches them.
Electron Configurations and Properties of Transition metals
Transition metals: electron configurations of d-block atoms and ions, the definition of a transition metal and variable oxidation states.
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Ligands, Complex Ions and Their Shapes
Ligands and complex ions: co-ordinate bonds, co-ordination number, bidentate and multidentate ligands and the shapes of complexes.
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Stereoisomerism in Complex Ions
Stereoisomerism in transition metal complexes: cis–trans and optical isomers, including cis-platin.
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Colour of Transition metal Ions
The colour of transition metal ions: d-orbital splitting, absorption of visible light and the effect of oxidation state, ligand and co-ordination number.
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Ligand substitution and the Stability of Complexes
Ligand substitution in copper(II) and cobalt(II) complexes, the chelate effect and entropy.
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Redox Chemistry of Transition metals
Transition metal redox reactions: vanadium oxidation states and colour changes.
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Redox Titrations with Transition metal Ions
Redox titrations of Fe²⁺ and C₂O₄²⁻ with MnO₄⁻: equations, ratios and calculations.
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Heterogeneous Catalysis
Transition metals as heterogeneous catalysts: surface adsorption, V₂O₅ in the Contact process.
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Homogeneous Catalysis and Autocatalysis
Homogeneous catalysis: Fe²⁺ with I⁻ and S₂O₈²⁻, and autocatalysis by Mn²⁺ in the MnO₄⁻ and C₂O₄²⁻ reaction.
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Complexes and Colour Map
AQA A-level Chemistry · 3.2.5 Complexes and colour
The whole section on one A4 page: transition metals, ligands, multidentate ligands and haem, isomers, colour and colorimetry.
Exchange and Catalysis Map
AQA A-level Chemistry · 3.2.5 Exchange, vanadium and catalysis
The whole section on one A4 page: ligand exchange, the chelate effect, vanadium, Tollens' reagent and heterogeneous and homogeneous catalysts.
Redox Titrations Map
AQA A-level Chemistry · 3.2.5.5 Redox titrations
The whole section on one A4 page: manganate(VII) with iron(II), the titration itself, other reducing agents, the choice of acid, similar redox titrations and the calculation.
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3.2.5.1
- i
know that transition metal characteristics of elements Ti-Cu arise from an incomplete d sub-level in atoms or ions
Revise - iii
know that a ligand is a molecule or ion that forms a co-ordinate bond with a transition metal by donating a pair of electrons
Revise - v
know that co-ordination number is the number of co-ordinate bonds to the central metal atom or ion
Revise
3.2.5.2
- ii a
know that exchange of NH3 ligands occurs without change of co-ordination number in examples such as Co2+ and Cu2+
Revise - ii b
know that exchange of H2O ligands occurs without change of co-ordination number in examples such as Co2+ and Cu2+
Revise - iv c
know that exchange of H2O by Cl- can involve a change of co-ordination number in examples such as Co2+, Cu2+ and Fe3+
Revise - vii
know that carbon monoxide is toxic because it replaces oxygen co-ordinately bonded to Fe(II) in haemoglobin
Revise - viii
know that bidentate and multidentate ligands replace monodentate ligands from complexes (the chelate effect)
Revise
3.2.5.3
3.2.5.4
- ii
understand that colour arises when some wavelengths of visible light are absorbed and the remaining wavelengths are transmitted or reflected
Revise - iii
know that d electrons move from the ground state to an excited state when light is absorbed
Revise - iv
know that the energy difference between ground and excited states is given by DeltaE = hv = hc/lambda
Revise - vi
know that a simple colorimeter can be used to determine the concentration of coloured ions in solution
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3.2.5.5
- ii a
know that vanadium species in oxidation state IV are formed by reduction of vanadate(V) ions by zinc in acidic solution
Revise - ii b
know that vanadium species in oxidation state III are formed by reduction of vanadate(V) ions by zinc in acidic solution
Revise - ii c
know that vanadium species in oxidation state II are formed by reduction of vanadate(V) ions by zinc in acidic solution
Revise - iii
know that the redox potential for a transition metal ion changing oxidation state is influenced by pH and by the ligand
Revise - iv
know that the reduction of [Ag(NH3)2]+ (Tollens' reagent) to metallic silver is used to distinguish between aldehydes and ketones
Revise - v
perform calculations for the redox titrations of Fe2+ and C2O42- with MnO4- and similar redox reactions
Revise
3.2.5.6
- ii
know that a heterogeneous catalyst is in a different phase from the reactants and the reaction occurs at active sites on the surface
Revise - iii
know the use of a support medium to maximise the surface area of a heterogeneous catalyst and minimise cost
Revise - iv
know that V2O5 acts as a heterogeneous catalyst in the Contact process and explain with equations how it does so
Revise - vi
know that heterogeneous catalysts can become poisoned by impurities that block the active sites
Revise - vii
know that a homogeneous catalyst is in the same phase as the reactants and the reaction proceeds through an intermediate species
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