Chemistry of transition elements: past paper questions

Where the questions come from

• Question 5May/June 2026, paper 41Structured13 marks

  Cobalt is a transition element. It forms a wide range of coloured compounds that contain ${\text{Co}}^{2+}$ ions or ${\text{Co}}^{3+}$ ions. Explain why a transition element, such as cobalt, has variable oxidation states in its compounds.

  Try this question
• Question 2Oct/Nov 2025, paper 41Structured8 marks

  Iron can form stable ions in the +2 and +3 oxidation states. Explain why transition elements have variable oxidation states.

  Try this question
• Question 4Oct/Nov 2023, paper 41Structured7 marks

  Cobalt(II) nitrate, $\mathrm{C}\mathrm{o}(\mathrm{N}{\mathrm{O}}_3{)}_2$, is a reddish-brown crystalline solid. It dissolves in water to form a solution containing $[\mathrm{C}\mathrm{o}({\mathrm{H}}_2\mathrm{O}{)}_6{]}^{2+}$ complex ions.

  Try this question
• Question 6May/June 2026, paper 41Structured8 marks

  Transition elements form complexes with species called ligands. The ethanedioate ion, ${\text{C}}_2{\text{O}}_4^{2-}$, is a bidentate ligand. Explain what is meant by bidentate ligand.

  Try this question
• Question 5Oct/Nov 2025, paper 41Structured14 marks

  Copper shows typical properties of transition elements, including its behaviour as a catalyst. Complete Table 5.1 to show the total number of unpaired electrons in the 3d and 4s orbitals of an isolated gaseous Cu atom and a ${\text{Cu}}^{2+}$ ion.

  Try this question
• Question 4Oct/Nov 2024, paper 41Structured12 marks

  Transition metal atoms and transition metal ions form complexes by combining with ligands. Explain why transition elements form complex ions.

  Try this question
• Question 5Oct/Nov 2023, paper 41Structured12 marks

  Transition elements behave as catalysts and can form complex ions. Explain why transition elements behave as catalysts.

  Try this question
• Question 1May/June 2026, paper 42Structured20 marksHas a diagram

  Transition elements have variable oxidation states and form complex ions. State two other typical chemical properties of a transition element.

  Try this question
• Question 5Oct/Nov 2024, paper 41Structured6 marksHas a diagram

  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 monodentate ligand.

  Try this question
• Question 6Oct/Nov 2023, paper 41Structured6 marks

  Five ligands are listed in Table 6.1.

  Try this question
• Question 6Oct/Nov 2025, paper 42Structured7 marks

  Nickel forms complexes. Give the formula and charge of the tetrahedral complex formed by $\mathrm{N}\mathrm{i}$ atoms with carbon monoxide molecules.

  Try this question
• Question 4Oct/Nov 2024, paper 42Structured12 marks

  Transition metal atoms and transition metal ions form complexes by combining with species called ligands.

  Try this question
• Question 5Oct/Nov 2024, paper 42Structured6 marksHas a diagram

  ${\text{Ni}}^{2+}$ ions form a number of different complex ions, including $[\text{Ni}({\text{H}}_2\text{O}{)}_6{]}^{2+}$, $[\text{Ni}({\text{NH}}_3{)}_6{]}^{2+}$ and $[\text{Ni}(\text{en}{)}_3{]}^{2+}$. The abbreviation en represents 1,2-diaminoethane.

  Try this question
• Question 6Oct/Nov 2023, paper 42Structured10 marksHas a diagram

  Phosphine, $:\mathrm{P}{\mathrm{H}}_3$, and carbon monoxide, $:\mathrm{C}\mathrm{O}$, are monodentate ligands found in some transition element complexes. Define monodentate ligand.

  Try this question
• Question 3Oct/Nov 2024, paper 43Structured16 marks

  $\mathbf{A}$ and $\mathbf{B}$ react together to give product $\mathrm{A}\mathrm{B}$.

  Try this question
• Question 5May/June 2025, paper 41Structured15 marks

  Copper is a transition element. Complete the electronic configurations of a $\mathrm{C}{\mathrm{u}}^{+}$ ion and a $\mathrm{C}{\mathrm{u}}^{2+}$ ion.

  Try this question
• Question 6May/June 2025, paper 41Structured8 marksHas a diagram

  Iron forms complex ions with the monodentate ligand, $\mathrm{C}{\mathrm{N}}^{-}$. Complex ion A contains one $\mathrm{F}{\mathrm{e}}^{3+}$ ion and six $\mathrm{C}{\mathrm{N}}^{-}$ ligands. Complex ion B contains one $\mathrm{F}{\mathrm{e}}^{2+}$ ion and six $\mathrm{C}{\mathrm{N}}^{-}$ ligands.

  Try this question
• Question 2May/June 2025, paper 42Structured17 marksHas a diagram

  When cobalt(II) sulfate, $\mathrm{C}\mathrm{o}\mathrm{S}{\mathrm{O}}_4$, is dissolved in distilled water, solution A is formed.

  Try this question
• Question 2May/June 2024, paper 41Structured12 marksHas a diagram

  Define transition element.

  Try this question
• Question 1May/June 2023, paper 41Structured19 marksHas a diagram

  Group 2 nitrates decompose when heated. Describe how the thermal stability of Group 2 nitrates changes with increasing proton number.

  Try this question
• Question 5May/June 2025, paper 43Structured15 marks

  Copper is a transition element. Complete the electronic configurations of a ${\mathrm{C}\mathrm{u}}^{+}$ ion and a ${\mathrm{C}\mathrm{u}}^{2+}$ ion.

  Try this question
• Question 3May/June 2024, paper 41Structured13 marksHas a diagram

  When a sample of hydrated lithium ethanedioate, $\mathrm{L}{\mathrm{i}}_2{\mathrm{C}}_2{\mathrm{O}}_4\cdot {\mathrm{H}}_2\mathrm{O}$, is gently heated, two gaseous products are formed and a white solid residue remains. The residue is added to $\mathrm{H}\mathrm{N}{\mathrm{O}}_3(\mathrm{a}\mathrm{q})$. A gas is produced that turns limewater milky.

  Try this question
• Question 2May/June 2023, paper 41Structured11 marksHas a diagram

  Some transition element complexes can show stereoisomerism.

  Try this question
• Question 6May/June 2025, paper 43Structured8 marksHas a diagram

  Iron forms complex ions with the monodentate ligand, ${\mathrm{C}\mathrm{N}}^{-}$. Complex ion A contains one ${\mathrm{F}\mathrm{e}}^{3+}$ ion and six ${\mathrm{C}\mathrm{N}}^{-}$ ligands. Complex ion B contains one ${\mathrm{F}\mathrm{e}}^{2+}$ ion and six ${\mathrm{C}\mathrm{N}}^{-}$ ligands.

  Try this question
• Question 4May/June 2024, paper 42Structured14 marksHas a diagram

  Explain why transition elements have variable oxidation states.

  Try this question
• Question 2May/June 2023, paper 42Structured12 marksHas a diagram

  State two typical chemical properties of a transition element.

  Try this question