Transition elements — AS & A Level Chemistry (9701) questions by topic
Ligand bonding and complex-ion geometry sit at the centre of this topic: classifying monodentate, bidentate and polydentate ligands, deducing complex-ion formulae for iron with cyanide, and explaining why transition elements form complexes using vacant, energetically accessible d-orbitals.
State, calculate, deduce, explain and express are the top command words across 25 questions from 2023 to 2025 papers, worth from 6 to 17 marks, so a single omitted term can strip marks from an otherwise complete answer. Instant marking after each response shows precisely which part of a bonding explanation or diagram was incomplete, rather than letting the same gap resurface in coordination-number or isomerism questions later.
What examiners look for
- Examiners repeatedly found 'energetically accessible' the phrase most often omitted when explaining why transition elements form complex ions.
- A common error was suggesting EDTA4- is bidentate rather than polydentate, and thinking Ni(PH3)2Cl2 is square planar when the data show it lacks cis-trans isomerism.
- Reports note poor diagrams using mixed 3D-bond conventions, distorted bond angles, or an incorrect tetrahedral three-dimensional drawing.
- A recurring criticism is stating a coordination number of six instead of eight, missing that each bidentate diars ligand contributes two bonds alongside four chloride ligands.
- Strong answers stated a correct definition of a tridentate ligand and completed the ligand-type table correctly.
May–June 2025, Paper 41
Copper is a transition element. (i) Complete the electronic configurations of a Cu+ ion and a Cu2+ ion. Cu+ ion: [Ar] ... Cu2+ ion: [Ar] ... (ii) Explain why transition elements…
Answer this question and get it marked →Iron forms complex ions with the monodentate ligand, CN−. Complex ion A contains one Fe3+ ion and six CN− ligands. Complex ion B contains one Fe2+ ion and six CN− ligands. (i)…
Answer this question and get it marked →May–June 2025, Paper 42
CoSO4 solution is added to excess NaOH solution. (i) State the colour of the precipitate formed when NaOH is first added to CoSO4. (ii) Write an ionic equation for the reaction of…
Answer this question and get it marked →May–June 2025, Paper 43
Copper is a transition element. (i) Complete the electronic configurations of a Cu⁺ ion and a Cu²⁺ ion. Cu⁺ ion: [Ar] ... Cu²⁺ ion: [Ar] ... (ii) Explain why transition elements…
Answer this question and get it marked →Iron forms complex ions with the monodentate ligand, CN⁻. Complex ion A contains one Fe³⁺ ion and six CN⁻ ligands. Complex ion B contains one Fe²⁺ ion and six CN⁻ ligands. (i)…
Answer this question and get it marked →May–June 2024, Paper 41
(i) Define transition element. (ii) Explain why transition elements can form complex ions.
Answer this question and get it marked →May–June 2024, Paper 42
(i) Explain why transition elements have variable oxidation states. (ii) Sketch the shape of a 3d(z2) orbital on a set of x, y, z axes.
Answer this question and get it marked →May–June 2024, Paper 43
(i) Define transition element. (ii) Explain why transition elements can form complex ions.
Answer this question and get it marked →October–November 2024, Paper 41
Transition metal atoms and transition metal ions form complexes by combining with ligands. (a) Explain why transition elements form complex ions.
Answer this question and get it marked →The shapes of four different complexes, P, Q, R and S, are shown in Table 5.1. The symbol J represents an atom or ion of a transition element. The symbol L is used to represent a…
Answer this question and get it marked →October–November 2024, Paper 42
Transition metal atoms and transition metal ions form complexes by combining with species called ligands. (a) When NaOH(aq) is added to an aqueous solution containing [Co(H2O)6]2+…
Answer this question and get it marked →Ni2+ ions form a number of different complex ions, including [Ni(H2O)6]2+, [Ni(NH3)6]2+ and [Ni(en)3]2+. The abbreviation en represents 1,2-diaminoethane. The numerical values of…
Answer this question and get it marked →October–November 2024, Paper 43
Transition metal atoms and transition metal ions form complexes by combining with ligands. (a) Explain why transition elements form complex ions.
Answer this question and get it marked →The shapes of four different complexes, P, Q, R and S, are shown in Table 5.1. The symbol J represents an atom or ion of a transition element. The symbol L is used to represent a…
Answer this question and get it marked →February–March 2023, Paper 42
Vanadium is a transition element in Period 4 of the Periodic Table. Define transition element.
Answer this question and get it marked →May–June 2023, Paper 42
State two typical chemical properties of a transition element.
Answer this question and get it marked →May–June 2023, Paper 43
The exhaust systems of most modern gasoline-fuelled cars contain a catalytic converter with three metal catalysts. These metals act as heterogeneous catalysts. Name three metal…
Answer this question and get it marked →October–November 2023, Paper 41
Cobalt(II) nitrate, Co(NO₃)₂, is a reddish-brown crystalline solid. It dissolves in water to form a solution containing [Co(H₂O)₆]²⁺ complex ions. Complete Table 4.1 giving the…
Answer this question and get it marked →Transition elements behave as catalysts and can form complex ions. Explain why transition elements behave as catalysts.
Answer this question and get it marked →Five ligands are listed in Table 6.1: NH₃, EDTA⁴⁻, CN⁻, H₂NCH₂CH₂NHCH₂CH₂NH₂ (given as tridentate), C₂O₄²⁻. Complete Table 6.1 using the words monodentate, bidentate and…
Answer this question and get it marked →October–November 2023, Paper 42
The structure of the polydentate ligand EDTA⁴⁻ is shown in Fig. 4.1 (a hexadentate ligand with two N atoms and four carboxylate O donor atoms). The stability constants at 298 K of…
Answer this question and get it marked →Phosphine, :PH₃, and carbon monoxide, :CO, are monodentate ligands found in some transition element complexes. Define monodentate ligand.
Answer this question and get it marked →October–November 2023, Paper 43
Cobalt(II) nitrate, Co(NO₃)₂, is a reddish-brown crystalline solid. It dissolves in water to form a solution containing [Co(H₂O)₆]²⁺ complex ions. Complete Table 4.1 giving the…
Answer this question and get it marked →Transition elements behave as catalysts and can form complex ions. Explain why transition elements behave as catalysts.
Answer this question and get it marked →Five ligands are listed in Table 6.1: NH₃, EDTA⁴⁻, CN⁻, H₂NCH₂CH₂NHCH₂CH₂NH₂ (given as tridentate), C₂O₄²⁻. Complete Table 6.1 using the words monodentate, bidentate and…
Answer this question and get it marked →Other AS & A Level Chemistry topics
- Practical skills (106)
- Hydrocarbons (65)
- Chemical bonding (63)
- The Periodic Table: chemical periodicity (59)
- Chemical energetics (53)
- Equilibria (53)
- Introduction to organic chemistry (53)
- Reaction kinetics (52)
- Carboxylic acids and derivatives (52)
- Group 2 (51)
- Carbonyl compounds (45)
- Atomic structure (44)