Transition metals and complex ions: Edexcel International A Level Chemistry questions

Every Edexcel International A Level Chemistry exam question on Transition metals and complex ions (specification points 17.1–17.17), 2019–2025, with its mark scheme and examiner’s report.

All 114 questions on Transition metals and complex ions, as a list

June 2025, Unit 5, Q4 (1 mark): 2+ ion? 4 What is the electronic configuration of a Zn 10 A [Ar] 3d 10 4s 2 B [Ar] 3d 9 4s 1 C [Ar] 3d 8 4s 2 D [Ar] 3d
June 2025, Unit 5, Q6 (1 mark): Which is incorrect for H2O, OH − and NH3? A all can act as bidentate ligands B all can act as electron pair donors C all can form dative covalent bonds D all ca
June 2025, Unit 5, Q15(a) (1 mark): State the shape of the cis-platin complex. (1)
June 2025, Unit 5, Q15(b) (1 mark): Draw the isomer trans-platin. (1)
June 2025, Unit 5, Q15(d)(i) (1 mark): DNA acts as a ligand in the formation of the complex shown in the diagram. Name this type of ligand. (1)
June 2025 (A), Unit 5, Q5 (1 mark): The aqueous solution of a transition metal ion is colourless. Which is the electronic configuration of this ion? A [Ar] 3d8 B [Ar] 3d10 C [Ar] 3d54s1 D [Ar] 3d1
June 2025 (A), Unit 5, Q6 (1 mark): Excess aqueous silver nitrate is added to a solution containing 0.100 mol of chromium(III) chloride, CrCl3•6H2O. A precipitate, AgCl, appears immediately, which
June 2025 (A), Unit 5, Q7(a) (1 mark): Which complex has a tetrahedral structure? (1) A [CrCl4]– B [Cu(NH3)4(H2O)2]2+ C [Pt(NH3)2Cl2] D [TiCl6]2–
June 2025 (A), Unit 5, Q7(b) (1 mark): Which complex contains a metal in the +1 oxidation state? (1) A [CuCl2]– B [CrCl4]– C [Pt(NH3)2Cl2] D [Ni(CO)4]
June 2025 (A), Unit 5, Q8 (1 mark): When EDTA4– is added to an aqueous solution of iron(III) ions, the EDTA complex is formed. Which is the best explanation for this? A iron(III) ions form stronge
June 2025 (A), Unit 5, Q16(a)(i) (1 mark): Draw the shape of this complex ion. (1)
June 2025 (A), Unit 5, Q16(a)(ii) (2 marks): Describe the bonding between the manganese(II) ion and the ligands. (2)
June 2025 (A), Unit 5, Q16(a)(iii) (3 marks): Explain why [Mn(H2O)6]2+ ions are coloured. (3)
January 2025, Unit 5, Q1 (1 mark): Which species cannot act as a ligand in the formation of a complex ion? A C2H6 B CO C OH– D C4H9NH2
January 2025, Unit 5, Q2 (1 mark): An aqueous solution of a transition metal ion absorbs frequencies of light corresponding to green, yellow and red. Which ion is likely to be in the solution? A
January 2025, Unit 5, Q3 (1 mark): The first five ionisation energies of four elements are shown. Which are the ionisation energies of a transition metal? A 419 3051 4412 5877 7975 B 578 1817 274
January 2025, Unit 5, Q6 (1 mark): Which of these pairs of elements are both transition metals? A gold and scandium B gold and titanium C scandium and zinc D titanium and zinc
January 2025, Unit 5, Q7 (1 mark): What are the shapes of the complexes [CuCl4]2– and Pt(NH3)2Cl2? [CuCl4]2– Pt(NH3)2Cl2 A square planar square planar B square planar tetrahedral C tetrahedral sq
January 2025, Unit 5, Q20(b)(i) (1 mark): Deduce the simplest formula of this double salt. (1)
January 2025, Unit 5, Q20(c)(ii) (2 marks): EDTA4– has been considered as a potential treatment for Cr3+ poisoning. O –O O –O N N O– O– O O EDTA4– Suggest how EDTA4– would act to treat Cr3+ poisoning, giv
January 2025, Unit 5, Q21(a)(i) (1 mark): The electronic configuration for Fe is shown. (1) Fe [Ar] 3d 4s Complete the electronic configuration for the Fe2+ ion in iron(II) sulfate. Fe2+ [Ar] 3d 4s
January 2025, Unit 5, Q21(a)(ii) (3 marks): An aqueous solution of iron(II) sulfate is pale green in colour. When left exposed to the air the solution turns brown. Explain why this colour change occurs. I
October 2024, Unit 5, Q1 (1 mark): What is the electronic configuration of the chromium atom? A [Ar] 3d4 4s2 B [Ar] 3d5 4s1 C [Ar] 3d6 D [Ar] 3d1 4s2 4p3
October 2024, Unit 5, Q2 (1 mark): Which ion shows the typical property of transition metals by forming coloured complexes? A Cu+ B Ni2+ C Sc3+ D Zn2+
October 2024, Unit 5, Q18(a)(i) (3 marks): Explain why the [Fe(H2O)6]2+ complex ion is coloured. (3)
October 2024, Unit 5, Q18(a)(ii) (2 marks): Explain why the two iron complex ions are different colours. (2)
October 2024, Unit 5, Q18(b)(ii) (3 marks): 12.8 cm3 of 0.05 mol dm−3 iron(III) chloride solution reacted with 8.0 cm3 of 0.08 mol dm−3 ammonium thiocyanate to form a complex ion. Deduce the formula of th
October 2024, Unit 5, Q18(c)(i) (3 marks): Plot a graph of absorbance against concentration using the data in the table. (3)
October 2024, Unit 5, Q18(c)(ii) (2 marks): 50.0 cm3 of a solution of copper(II) sulfate of unknown concentration was pipetted into a 250.0 cm3 volumetric flask and the volume made up to the mark with dei
October 2024, Unit 5, Q18(d)(i) (1 mark): Give a reason, by referring to the equation, why the formation of the diamine complex from the aqueous complex ion is thermodynamically favoured. (1)
October 2024, Unit 5, Q18(d)(ii) (2 marks): Explain, by reference to the structure of ethane-1,2-diamine, why it is a bidentate ligand. (2)
October 2024, Unit 5, Q18(d)(iii) (3 marks): Explain how the H N H bond angles would be expected to change in ethane-1,2-diamine when the complex ion is formed. (3)
June 2024, Unit 5, Q16(b)(i) (3 marks): Complete the table for the complex. (3) Charge on nickel ion Type of ligand Co‑ordination number of the nickel ion Shape of metal complex around the nickel ion
June 2024, Unit 5, Q16(b)(ii) (2 marks): Explain, using a balanced equation, why the formation of the dimethyldithiocarbamate complex from an aqueous solution of nickel ions is thermodynamically feasib
January 2024, Unit 5, Q3 (1 mark): Which successive ionisation energies (in kJ mol–1) are most likely to be those of a transition element? A 578 1817 2745 11 578 14 831 B 759 1561 2958 5290 7236
January 2024, Unit 5, Q5(a) (1 mark): What are the electronic structures of the three copper species? (1) Cu+ Cu2+ Cu [Ar] 3d9 4s2 [Ar] 3d9 4s1 [Ar] 3d9 A [Ar] 3d9 4s2 [Ar] 3d8 4s2 [Ar] 3d7 4s2 B [A
January 2024, Unit 5, Q17(a)(i) (3 marks): Explain why the three isomers have different colours. (3)
January 2024, Unit 5, Q17(a)(ii) (5 marks): You are provided with three equimolar solutions of the three isomers. Suggest how you would quantitatively determine the relative numbers of free chloride ions
January 2024, Unit 5, Q17(b)(ii) (1 mark): Describe how guanine and adenine can bind to the platinum ion. (1)
January 2024, Unit 5, Q17(b)(iii) (2 marks): trans‑Platin binds to DNA. Suggest why this does not damage the DNA. (2)
January 2024, Unit 5, Q17(c)(i) (3 marks): Calculate the values x, y and z in Reinecke’s salt. You must show your working. (3)
January 2024, Unit 5, Q17(c)(ii) (2 marks): Draw a diagram of the anion of Reinecke’s salt showing its three‑dimensional shape. (2)
January 2024, Unit 5, Q17(d)(i) (2 marks): Explain why the tetrahedral complex [Co(NH3)ClBrI] exists as two optical isomers. (2)
January 2024, Unit 5, Q17(d)(ii) (1 mark): Complete the diagram showing the two optical isomers of the tetrahedral complex. (1) Co Co
October 2023, Unit 5, Q1 (1 mark): Which of these is a d-block element but is not a transition element? A cobalt B copper C nickel D zinc
October 2023, Unit 5, Q3 (1 mark): What is the co-ordination number of chromium in the complex ion shown? + Cl H2N NH2 H2C CH2 Cr H2C CH2 H2N NH2 Cl A 2 B 3 C 4 D 6
October 2023, Unit 5, Q19(c)(i) (2 marks): Explain how water acts as a monodentate ligand. (2)
October 2023, Unit 5, Q19(c)(ii) (2 marks): Explain the shape of the [Fe(H2O)6]2+ complex ion. (2)
October 2023, Unit 5, Q19(d) (2 marks): Haemoglobin is an iron(II) complex which carries oxygen around the body. Part of the structure of oxyhaemoglobin is shown. O2 N N Fe2+ N N globin The four nitro
October 2023, Unit 5, Q19(e) (2 marks): Ethanedioate ligands react with iron(II) ions in aqueous solution. 2− → [Fe(C2O4)2 (H2O)2]2− + 4H2O [Fe(H2O)6]2+ + 2C2O4 Explain, in terms of entropy, why this
June 2023, Unit 5, Q6 (1 mark): Which electronic configuration is correct? A Ti2+ [Ar]4s2 B Cr [Ar]3d44s2 C Fe3+ [Ar]3d34s2 D Cu [Ar]3d104s1
June 2023, Unit 5, Q7 (1 mark): The structure of the complex Cr2(CH3CO2)4(H2O)2 is shown. CH3 C CH3 O O C O O H2O Cr Cr OH2 O O C O O CH3 C CH3 What is the coordination number of chromium in t
June 2023, Unit 5, Q8 (1 mark): Which complex contains only monodentate ligands? A [Fe(CN)6]4– B [Cr(C2O4)3]3– C [Ni(EDTA)]2– D [Co(NH2CH2CH2NH2)2Cl2]
June 2023, Unit 5, Q9 (1 mark): Which complex has a ligand-metal-ligand bond angle of 109.5°? A [CuCl4]2– B [Fe(EDTA)]– C [Ag(NH3)2]+ D [Pt(NH3)2Cl2]
June 2023, Unit 5, Q10 (1 mark): Which ion is not blue? A VO2+ B [Co(H2O)6]2+ C [Cr(H2O)6]2+ D [Cu(H2O)6]2+ Use this space for any rough working. Anything you write in this space will gain no c
June 2023, Unit 5, Q21(a) (3 marks): Mercury forms compounds in either the +1 or +2 oxidation states. Explain why mercury is classified as a d-block element but is not a transition element. (3)
January 2023, Unit 5, Q1 (1 mark): In which species does the transition metal have the lowest oxidation number? A [Cu(NH3)2]+ B [Fe(CN)6]3– C MnSO4 D Ni(CO)4
January 2023, Unit 5, Q2(a) (1 mark): What is the coordination number of chromium(III) in this complex ion? (1) A 2 B 3 C 4 D 6
January 2023, Unit 5, Q2(b) (1 mark): What is the overall charge on this complex ion? (1) A 0 B +1 C +2 D +3 Use this space for any rough working. Anything you write in this space will gain no credi
January 2023, Unit 5, Q3 (1 mark): Which complex ion is colourless? A [Al(H2O)6]3+ B [Cu(H2O)6]2+ C [Fe(H2O)6]3+ D [Ni(H2O)6]2+
January 2023, Unit 5, Q18(a) (1 mark): State the oxidation number of vanadium in Na3VO4 . (1)
January 2023, Unit 5, Q18(b) (3 marks): In aqueous solution, vanadium(II) exists as [V(H2O)6]2+ but vanadium(V) exists as [VO2(H2O)4]+. Explain why vanadium(V) does not exist as [V(H2O)6]5+. (3)
January 2023, Unit 5, Q20(a)(i) (1 mark): Complete the electronic configurations for a manganese atom and a manganese(II) ion, using the electron-in-boxes notation. (1) Mn atom: [Ar] 3d 4s Mn2+ ion: [Ar
January 2023, Unit 5, Q20(a)(ii) (3 marks): The standard electrode potentials, E , for the half-cells involving the oxidation states +3 and +2 for manganese and iron are shown. Mn3+(aq) + e–  Mn2+(aq) E
October 2022, Unit 5, Q5 (1 mark): The element zinc is not classified as a transition metal. This is because A the 3d subshell of a zinc atom is full B zinc only forms one stable ion C the only s
October 2022, Unit 5, Q6 (1 mark): What is the electronic configuration of the Fe2+ ion? A [Ar] ↑ ↑ ↑ ↑ ↑ ↑ B [Ar] ↑↓ ↑ ↑ ↑ ↑ C [Ar] ↑ ↑ ↑ ↑ ↑↓ D [Ar] ↑↓ ↑↓ ↑ ↑ 3d 4s
October 2022, Unit 5, Q7 (1 mark): Platinum forms a complex with the formula Pt(NH3)2Cl2 which is used in cancer treatment. Three possible structures of this complex are shown. Cl Cl NH NH3 Cl NH
October 2022, Unit 5, Q8 (1 mark): When oxygen binds to the haem group in haemoglobin, each oxygen molecule A bonds reversibly to an iron(II) ion B bonds irreversibly to an iron(II) ion C replace
October 2022, Unit 5, Q19(a) (3 marks): Explain the highest stable oxidation state formed by vanadium, by referring to its electronic configuration. (3)
October 2022, Unit 5, Q23(e)(i) (2 marks): Draw a diagram of the complex that one salen ligand forms with a Ni2+ ion, showing the type of bonding involved. (2)
October 2022, Unit 5, Q23(e)(ii) (2 marks): Explain why the salen ligand complex of the Ni2+ ion is much more stable than the aqua complex of the same ion. (2)
October 2022, Unit 6, Q1(a)(i) (1 mark): Note the A pink solution The formula of the complex (1) appearance ion formed is
June 2022, Unit 5, Q4 (1 mark): Which transition metal complex is commonly used as a treatment for cancer? 2– Cl A Cu Cu Cl Cl Cl + NCCH NCCH3 B Cu Cu NCCH NCCH3 H3CCN CCN NCCH NCCH3 Cl NH NH3
June 2022, Unit 5, Q15(c)(i) (3 marks): The structure of DPC is shown. O H H N N N N H H Describe how DPC is able to act as a bidentate ligand, using your diagram to show the atoms involved. (3)
June 2022, Unit 5, Q15(c)(ii) (1 mark): The intense colour of this complex is due to the transfer of electrons from the ligand to the chromium(VI) ion. Suggest a possible reason why the colour is not
January 2022, Unit 5, Q1(a) (1 mark): The bonding within the complex [Cu(NH3)4(H2O)2]2+ is (1) A covalent, dative covalent and ionic B covalent and dative covalent only C covalent only D dative cova
January 2022, Unit 5, Q1(b) (1 mark): Which complex is tetrahedral? (1) A [Pt(NH3)2Cl2] B [Cu(H2O)4(OH)2] C [Cu(NH3)4(H2O)2]2+ D [CoCl4]2−
January 2022, Unit 5, Q1(c) (1 mark): Which complex contains a bidentate ligand? (1) A [Co(NH2CH2CH2NHCH2CH2NH2)2]3+ B [Cu(NH3)4(H2O)2]2+ C [Ni(NH2CH2CH2NH2)3]2+ D [Mn(EDTA)]2− Use this space for ro
January 2022, Unit 5, Q9 (1 mark): The formulae of four ions are shown. Formula of ion 2− CrO4 AlO2 − [Fe(CN)6]4− [CrCl2(H2O)4]+ How many of these ions contain a metal with an oxidation number of
January 2022, Unit 5, Q10(a)(i) (3 marks): Explain the shape of [Ag(NH3)2]+ . (3)
January 2022, Unit 5, Q10(a)(ii) (2 marks): Explain why [Ag(NH3)2]+ is colourless. (2)
October 2021, Unit 5, Q5 (1 mark): Which of the following statements best explains carbon monoxide poisoning? A carbon monoxide binds irreversibly to haemoglobin B carbon monoxide forms stronger
October 2021, Unit 5, Q7 (1 mark): Some nickel(II) complex ions are formed by the addition of complexing agents to nickel(II) ions, [Ni(H2O)6]2+ , in aqueous solution. On formation, which of thes
October 2021, Unit 5, Q18(b) (1 mark): Give the formula of complex ion B. (1)
October 2021, Unit 5, Q18(c) (1 mark): Complex ion C has six cyanide ligands. Draw the structure of C, clearly showing its three‑dimensional shape. (1)
October 2021, Unit 5, Q20(b)(i) (2 marks): THF acts as a monodentate ligand in complex Y. State the meaning of the terms monodentate and ligand. (2)
October 2021, Unit 5, Q20(b)(ii) (1 mark): Complex Z is a stereoisomer of complex Y. Complete the diagram to show the arrangement of the ligands in complex Z. (1) Cl Ti3+ complex Z
October 2021, Unit 5, Q20(c)(vi) (6 marks): The student’s teacher said, 2+ ions are colourless in aqueous solution, the titration can “As TiCl3 is blue and TiO be carried out without an alizarin indicator
October 2021, Unit 5, Q21(c) (2 marks): Curcumin anions can act as bidentate ligands in metal‑curcumin (M‑curc) complexes. The oxygen atoms of the curc ligand occupy adjacent coordination sites in the
June 2021, Unit 5, Q3 (1 mark): What is the electronic configuration of a chromium atom? 3d 4s ↑ ↑ ↑ ↑ ↑ ↑ A (Ar) ↑ ↑ ↑ ↑ ⇅ B (Ar) ⇅ ⇅ ↑ ↑ C (Ar) ⇅ ↑ ↑ ⇅ D (Ar)
June 2021, Unit 5, Q4 (1 mark): A ligand must be an A electron-pair donor B electron-pair donor and negatively charged C electron-pair acceptor D electron-pair acceptor and negatively charged
June 2021, Unit 5, Q5 (1 mark): Diamminecopper(I) ions are not coloured because A the d orbitals in copper(I) cannot be split B the energy difference between the split d orbitals is outside t
June 2021, Unit 5, Q6 (1 mark): Copper(II) ions form a complex with 1,2-diaminoethane (symbol ‘en’) with the formula Cu(en)3 2+. What type of ligand is 1,2-diaminoethane, and what is the coord
June 2021, Unit 5, Q21(a) (2 marks): Explain, in terms of electronic structure, why iron(III) compounds are more stable than iron(II) compounds. (2)
June 2021, Unit 5, Q21(b)(ii) (3 marks): Explain how stable iron(III) ions can be formed from iron(II) ions in aqueous solution. Refer to the relevant energy changes of these ions only. (3)
June 2021, Unit 5, Q21(c) (3 marks): Invertebrates use a copper complex, haemocyanin, to transport oxygen. Blue oxyhaemocyanin gives invertebrate blood its characteristic colour. Explain why oxyhae
June 2021, Unit 5, Q21(d)(i) (4 marks): The presence of iron in sodium carbonate can affect its properties; the higher the quality of the sodium carbonate, the lower the proportion of iron. The propor
June 2021, Unit 5, Q21(d)(ii) (2 marks): Suggest what type of ligand thioglycolic acid is in the iron(III) thioglycolic acid complex. Justify your answer. (2)
June 2021, Unit 5, Q21(f) (1 mark): Give a possible reason why the chloro complexes of iron ions have a coordination number of four rather than six. (1)
January 2021, Unit 5, Q5 (1 mark): Which of these has the greatest number of unpaired electrons in each of its atoms? A chromium B iron C manganese D vanadium
January 2021, Unit 5, Q6 (1 mark): Nickel is classified as a transition metal. This is because nickel A is a d block element B has partially filled d orbitals C forms stable ions with partially f
January 2021, Unit 5, Q7(a) (1 mark): What are the shapes of these complexes? (1) A both complexes are square planar B both complexes are tetrahedral − is square planar C Pt(NH3)2Cl2 is tetrahedral
January 2021, Unit 5, Q7(b) (1 mark): What is the bonding between the ligands and the central atom in these complexes? (1) A the bonding in both complexes is ionic B the bonding in both complexes is
January 2021, Unit 5, Q8 (1 mark): Cobalt chloride is used as a test for the presence of water. This test depends on the fact that A anhydrous cobalt(II) chloride is blue and hydrated cobalt(II)
January 2021, Unit 5, Q19(b)(i) (1 mark): Name this type of chemical species. (1)
January 2021, Unit 5, Q19(b)(ii) (3 marks): Explain why T is coloured while V is colourless. A detailed explanation of the fact that T is coloured is not required. (3)
January 2021, Unit 6, Q1(b)(i) (1 mark): B is a blue solution. When A is added to B, the mixture first turns green and then gradually turns yellow. Give the formula of the cation in B. (1)
October 2020, Unit 5, Q16 (1 mark): The electronic configuration of the atoms of an element is 1s22s22p63s23p63d54s1. What is the maximum oxidation number shown in compounds of this element? A +1
October 2020, Unit 5, Q17 (1 mark): Which of the following species will not act as a ligand in the formation of a complex ion? A CH3NH2 B CN− C NH3 D NH4 +
October 2020, Unit 5, Q18 (1 mark): What is the coordination number of the nickel(II) ion and the overall charge, m, of this complex? m Cl O O C O O C Ni C O O C O O Cl Coordination number of Over
October 2020, Unit 5, Q24(a)(iii) (2 marks): Complete the diagram to show the structure of the complex ion formed in Reaction 3, showing all of the atoms. (2) Fe
October 2020, Unit 5, Q25(c)(ii) (1 mark): The Lanthanides The lanthanides form a series in the Periodic Table comprising the elements from lanthanum, La (Z = 57) to lutetium, Lu (Z = 71). They have impo
October 2020, Unit 5, Q25(d) (2 marks): The Lanthanides The lanthanides form a series in the Periodic Table comprising the elements from lanthanum, La (Z = 57) to lutetium, Lu (Z = 71). They have impo
October 2020, Unit 6, Q1(d) (1 mark): Give a possible reason why compound A is green. (1)

Questions, mark schemes and examiner’s reports are © Pearson Edexcel, from their published past papers. Plumi isn’t affiliated with any exam board. Want whole papers? Every Edexcel International A Level Chemistry paper.

Rather write your answers by hand on iPad? Plumi marks them against the same mark schemes.

4,117 questions