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Principles of transition metal chemistry: Edexcel A‑Level Chemistry questions

Every Edexcel A-Level Chemistry exam question on 15A Principles of transition metal chemistry, 2016–2025, with its mark scheme and examiner’s report.

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2,028 questions

  1. Q6(a)(i)

    June 2025 · Paper 1

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    June 2025 Paper 1, question 6(a)(i): Which pair of electronic configurations is correct? (1) Cr3+ Cr [Ar] 3d44s2 [Ar] 3d14s2 A [Ar] 3d54s1 [Ar] 3d14s2 B [Ar] 3d44s2 [Ar] 3d3 C D [Ar] 3d54s1 [Ar] 3d

  2. Q6(a)(ii)

    June 2025 · Paper 1

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    June 2025 Paper 1, question 6(a)(ii): State why chromium is classified as a transition metal. (1)

  3. Q6(b)(i)

    June 2025 · Paper 1

    2 marks15A Principles of transition metal chemistry
    The whole paper ↗
    June 2025 Paper 1, question 6(b)(i): Draw the structure of the complex ion, [Cr(H2O)6]3+(aq), showing clearly its 3‑dimensional shape, and the bonds between the chromium ion and the water ligands.

  4. Q6(b)(ii)

    June 2025 · Paper 1

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    June 2025 Paper 1, question 6(b)(ii): Name the shape of the [Cr(H2O)6]3+(aq) complex ion. (1)

  5. Q6(e)(i)

    June 2025 · Paper 1

    4 marks15A Principles of transition metal chemistry
    The whole paper ↗
    June 2025 Paper 1, question 6(e)(i): Explain why aqueous solutions of [Cr(H2O)6]3+ are coloured. (4)

  6. Q6(e)(ii)

    June 2025 · Paper 1

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    June 2025 Paper 1, question 6(e)(ii): Give the reason why the solutions of [Cr(H2O)6]3+ and [CrCl4]– are different colours. (1)

  7. Q5(a)(iii)

    June 2025 · Paper 3

    3 marks15A Principles of transition metal chemistry
    The whole paper ↗
    June 2025 Paper 3, question 5(a)(iii): Draw the three-dimensional shape of the complex ion, Q, using your answer to (a)(ii) to help deduce the formula and overall charge. (3)

  8. Q5(b)(ii)

    June 2025 · Paper 3

    3 marks15A Principles of transition metal chemistry
    The whole paper ↗
    June 2025 Paper 3, question 5(b)(ii): Explain, in terms of equilibria and entropy, which of the three complex ions is the most stable. (3)

  9. Q6

    June 2024 · Paper 1

    6 marks15A Principles of transition metal chemistry
    The whole paper ↗
    June 2024 Paper 1, question 6: *6 Explain why aqueous solutions of Cu2+ ions and Fe2+ ions are coloured but have different colours, whereas aqueous solutions of Zn2+ ions are colourless. Incl

  10. Q7(c)(i)

    June 2023 · Paper 1

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    June 2023 Paper 1, question 7(c)(i): State the colour of this complex ion. (1)

  11. Q7(c)(i)

    June 2023 · Paper 3

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    June 2023 Paper 3, question 7(c)(i): Complete the diagram to show how Eriochrome Black T forms three dative covalent or coordinate bonds with the calcium ion. (1) NO2 O O–Na+ S O N N O O H Ca2+ H

  12. Q7(c)(ii)

    June 2023 · Paper 3

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    June 2023 Paper 3, question 7(c)(ii): State the number of water molecules needed to complete this complex. (1)

  13. Q10(a)

    June 2023 · Paper 3

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    June 2023 Paper 3, question 10(a): The first step involves the reaction of nickel oxide with hydrogen gas at 473 K. NiO(s) + H2(g) → Ni(s) + H2O(g) The nickel is not pure because the impurities a

  14. Q7(a)

    June 2022 · Paper 1

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    June 2022 Paper 1, question 7(a): The common oxidation numbers of chromium are +2, +3 and +6. Give a reason, in terms of ionisation energies, why chromium can show variable oxidation numbers. (1

  15. Q7(c)(iv)

    June 2022 · Paper 1

    2 marks15A Principles of transition metal chemistry
    The whole paper ↗
    June 2022 Paper 1, question 7(c)(iv): Aqueous solutions containing chromium(III) ions and chromium(II) ions have different colours. Explain why these solutions differ in colour. An explanation of th

  16. Q2(a)(i)

    June 2022 · Paper 3

    4 marks15A Principles of transition metal chemistry
    The whole paper ↗
    June 2022 Paper 3, question 2(a)(i): The colour of the cobalt(II) sulfate solution used is pink due to the complex cobalt(II) ion, [Co(H2O)6]2+. Explain why the solution is coloured. (4)

  17. Q8(a)(i)

    November 2021 · Paper 1

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    November 2021 Paper 1, question 8(a)(i): Give a reason why the ammonium ion cannot act as a ligand. (1)

  18. Q8(a)(ii)

    November 2021 · Paper 1

    4 marks15A Principles of transition metal chemistry
    The whole paper ↗
    November 2021 Paper 1, question 8(a)(ii): Explain why the complex ions [Co(NH3)6]2+ and [Co(H2O)6]2+ are coloured and have different colours. (4)

  19. Q8(b)

    November 2021 · Paper 1

    1 mark15A Principles of transition metal chemistry
    The whole paper ↗
    November 2021 Paper 1, question 8(b): Which of these complexes is used in the treatment of cancer? (1) Cl Cl OH2 OH2 A B Pt Pt H2O Cl Cl OH2 Cl NH3 Cl OH2 C D Pt Pt Cl NH3 H3N Cl

  20. Q8(c)

    November 2021 · Paper 1

    4 marks15A Principles of transition metal chemistry
    The whole paper ↗
    November 2021 Paper 1, question 8(c): Compare and contrast the complex ions formed by cobalt(III) ions with the ligand ethane‑1,2‑diamine and with the ligand EDTA4–. Ignore any difference in colour.
All 42 questions on Principles of transition metal chemistry, as a list
  1. June 2025, Paper 1, Q6(a)(i) (1 mark): Which pair of electronic configurations is correct? (1) Cr3+ Cr [Ar] 3d44s2 [Ar] 3d14s2 A [Ar] 3d54s1 [Ar] 3d14s2 B [Ar] 3d44s2 [Ar] 3d3 C D [Ar] 3d54s1 [Ar] 3d
  2. June 2025, Paper 1, Q6(a)(ii) (1 mark): State why chromium is classified as a transition metal. (1)
  3. June 2025, Paper 1, Q6(b)(i) (2 marks): Draw the structure of the complex ion, [Cr(H2O)6]3+(aq), showing clearly its 3‑dimensional shape, and the bonds between the chromium ion and the water ligands.
  4. June 2025, Paper 1, Q6(b)(ii) (1 mark): Name the shape of the [Cr(H2O)6]3+(aq) complex ion. (1)
  5. June 2025, Paper 1, Q6(e)(i) (4 marks): Explain why aqueous solutions of [Cr(H2O)6]3+ are coloured. (4)
  6. June 2025, Paper 1, Q6(e)(ii) (1 mark): Give the reason why the solutions of [Cr(H2O)6]3+ and [CrCl4]– are different colours. (1)
  7. June 2025, Paper 3, Q5(a)(iii) (3 marks): Draw the three-dimensional shape of the complex ion, Q, using your answer to (a)(ii) to help deduce the formula and overall charge. (3)
  8. June 2025, Paper 3, Q5(b)(ii) (3 marks): Explain, in terms of equilibria and entropy, which of the three complex ions is the most stable. (3)
  9. June 2024, Paper 1, Q6 (6 marks): *6 Explain why aqueous solutions of Cu2+ ions and Fe2+ ions are coloured but have different colours, whereas aqueous solutions of Zn2+ ions are colourless. Incl
  10. June 2023, Paper 1, Q7(c)(i) (1 mark): State the colour of this complex ion. (1)
  11. June 2023, Paper 3, Q7(c)(i) (1 mark): Complete the diagram to show how Eriochrome Black T forms three dative covalent or coordinate bonds with the calcium ion. (1) NO2 O O–Na+ S O N N O O H Ca2+ H
  12. June 2023, Paper 3, Q7(c)(ii) (1 mark): State the number of water molecules needed to complete this complex. (1)
  13. June 2023, Paper 3, Q10(a) (1 mark): The first step involves the reaction of nickel oxide with hydrogen gas at 473 K. NiO(s) + H2(g) → Ni(s) + H2O(g) The nickel is not pure because the impurities a
  14. June 2022, Paper 1, Q7(a) (1 mark): The common oxidation numbers of chromium are +2, +3 and +6. Give a reason, in terms of ionisation energies, why chromium can show variable oxidation numbers. (1
  15. June 2022, Paper 1, Q7(c)(iv) (2 marks): Aqueous solutions containing chromium(III) ions and chromium(II) ions have different colours. Explain why these solutions differ in colour. An explanation of th
  16. June 2022, Paper 3, Q2(a)(i) (4 marks): The colour of the cobalt(II) sulfate solution used is pink due to the complex cobalt(II) ion, [Co(H2O)6]2+. Explain why the solution is coloured. (4)
  17. November 2021, Paper 1, Q8(a)(i) (1 mark): Give a reason why the ammonium ion cannot act as a ligand. (1)
  18. November 2021, Paper 1, Q8(a)(ii) (4 marks): Explain why the complex ions [Co(NH3)6]2+ and [Co(H2O)6]2+ are coloured and have different colours. (4)
  19. November 2021, Paper 1, Q8(b) (1 mark): Which of these complexes is used in the treatment of cancer? (1) Cl Cl OH2 OH2 A B Pt Pt H2O Cl Cl OH2 Cl NH3 Cl OH2 C D Pt Pt Cl NH3 H3N Cl
  20. November 2021, Paper 1, Q8(c) (4 marks): Compare and contrast the complex ions formed by cobalt(III) ions with the ligand ethane‑1,2‑diamine and with the ligand EDTA4–. Ignore any difference in colour.
  21. November 2021, Paper 1, Q8(d) (2 marks): Hydrated chromium(III) chloride, CrCl3.6H2O, dissolves in water to form a number of different complex ions containing both chloride and water ligands. The gener
  22. October 2020, Paper 1, Q1(e) (4 marks): A student stated that ‘the elements scandium and zinc are d-block elements but are not transition metals’. Discuss this statement, using appropriate electronic
  23. October 2020, Paper 1, Q3(b)(i) (1 mark): Give the shape of this complex ion. (1)
  24. October 2020, Paper 1, Q3(b)(ii) (3 marks): Explain why the chromium complex ion is coloured. (3)
  25. October 2020, Paper 1, Q3(c) (3 marks): The ligand ethylenediaminetetraacetate, EDTA4−, has the structure shown. O −O O O− N N −O O− O O When a solution of EDTA4− is added to a solution of [Cr(H2O)6]3
  26. October 2020, Paper 3, Q7 (6 marks): *7 “Cobalt(II) ions combine with substances in solution to form complex ions with different coordination numbers.” Discuss this statement by referring to two co
  27. June 2019, Paper 1, Q7 (6 marks): *7 Colour is often used in chemistry to identify substances. Compare and contrast the origin of the colour of a copper(II) complex with the origin of the colour
  28. June 2019, Paper 3, Q6(a)(i) (1 mark): State the coordination number of Cr3+ in this complex ion. (1)
  29. June 2019, Paper 3, Q6(a)(ii) (1 mark): State the overall charge on this complex ion. (1)
  30. June 2019, Paper 3, Q6(b) (3 marks): The complex ions of transition metals have different colours in aqueous solution. Two factors that affect the colour of the solution are the oxidation number of
  31. June 2019, Paper 3, Q9(a)(ii) (2 marks): A hot aqueous solution of glycine is added to a hot solution of copper(II) ethanoate. When the mixture is cooled, crystals of copper(II) glycinate are formed. W
  32. June 2019, Paper 3, Q9(b) (2 marks): Haemoglobin is an iron(II) complex. It carries oxygen around the body. Part of the structure of haemoglobin is shown. O2 N N Fe2+ N N globin The four nitrogen a
  33. June 2018, Paper 1, Q4(a) (1 mark): Which of these ions has the electronic configuration [Ar]3d5? (1) A Cr3+ B Fe2+ C Mn2+ D Mn3+
  34. June 2018, Paper 1, Q4(b) (1 mark): In which of these complex ions does the transition metal have the oxidation number +3? (1) A [Ag(CN)2]− B [CuCl4]2− C [Fe(CN)6]3− D [Ni(EDTA)]2−
  35. June 2018, Paper 1, Q4(c) (1 mark): Which type or types of bonding exist within the complex ion [Cr(H2O)6]3+? (1) A dative covalent only B dative covalent and covalent only C dative covalent and i
  36. June 2018, Paper 1, Q4(d) (1 mark): Which best explains why [Cu(NH3)2]+ ions are colourless? (1) A all complex ions having a metal ion with a +1 charge are colourless B no electronic transitions c
  37. June 2018, Paper 1, Q4(e) (2 marks): Glycinate ions are bidentate ligands and can be represented by the structure O H2N CH2 C O− Complete the diagram below to show the structure of the [Cu(NH2CH2CO
  38. June 2017, Paper 1, Q4(a) (1 mark): Which of these is the electronic configuration of an iron(II) ion, Fe2+? (1) 3d 4s np np np A [Ar] np n n n n B [Ar] np np np C [Ar] n n n n np D [Ar]
  39. June 2017, Paper 1, Q4(b) (2 marks): Iron(II) ions, [Fe(H2O)6]2+, form a pale green solution but zinc ions, [Zn(H2O)6]2+, form a colourless solution. Explain why zinc ions are colourless. (2)
  40. June 2017, Paper 1, Q4(c)(i) (2 marks): Draw a structure of the [Fe(C2O4)2(H2O)2]2– ion, showing all of the bonds. (2)
  41. June 2017, Paper 1, Q4(c)(ii) (2 marks): Explain, in terms of entropy, why this reaction is feasible. (2)
  42. June 2017, Paper 3, Q7(a) (6 marks): Many of the d-block elements are also classified as transition metals. Explain why two of the d-block elements within Period 4 (scandium to zinc) are not classi

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