AS & A Level Chemistry 9701 · Topic 28

Chemistry of transition elements: past paper questions

139 real questionsasked in 8 of the last 10 exam series2019–2026usually: Explain, Define, State, Complete, Suggest

Real questions on chemistry of transition elements

The newest 20 of 138 written questions, plus 1 multiple-choice. Open one to see it on the real paper.

9701/41 · May/June 2026 · Q6c[2]
Hg 2+ ions and iodide ions, I – , form a complex with the formula [HgI 4 ] 2– . Write the expression for K stab of [HgI 4 ] 2– . State its units. K stab = units =
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9701/41 · October/November 2025 · Q5b[2]
The 3d orbitals in an isolated Cu 2+ ion are degenerate. Complete the diagram to show the relative energies of the 3d orbitals in an isolated Cu 2+ ion and in Cu 2+ in a tetrahedral complex. energy isolated Cu 2+ ion Cu 2+ in a tetrahedral complex
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9701/41 · October/November 2025 · Q5c[2]
Explain why transition elements behave as catalysts.
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9701/42 · May/June 2025 · Q2a(i)[4]
Complete Table 2.1 to show the formula and colour of each of the cobalt-containing species present in A, B and C. Identify the type of reaction forming each of B and C. Table 2.1 formula of cobalt-containing species colour of cobalt-containing species type of reaction A B C
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9701/42 · May/June 2025 · Q2a(ii)[1]
Suggest a suitable reagent for the formation of [CoCl 4 ] 2– from solution A.
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9701/42 · May/June 2025 · Q2b(i)[2]
Complete Fig. 2.2 to show the relative energies of the 3d orbitals in an isolated Co 2+ ion and in Co 2+ in a tetrahedral complex. energy isolated Co 2+ ion Co 2+ in a tetrahedral complex
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9701/42 · February/March 2025 · Q1a[1]
Silver can form compounds containing either Ag + or Ag 2+ ions. Explain why silver is a transition element.
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9701/42 · February/March 2025 · Q3a(i)[1]
Define complex.
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9701/42 · October/November 2024 · Q4a(i)[1]
State the colour change seen in this precipitation reaction. from to
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9701/42 · October/November 2024 · Q4a(ii)[1]
Complete the ionic equation for this precipitation reaction. 2+
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9701/42 · October/November 2024 · Q4b(i)[1]
Give the formula of E.
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9701/42 · October/November 2024 · Q4b(ii)[1]
Identify the oxidation state of cobalt in E.
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9701/42 · October/November 2024 · Q4b(iii)[1]
The d-orbitals of the cobalt atom or ion present in E are split in energy. State the number of d-orbitals that are at a higher energy level and the number of d-orbitals that are at a lower energy level. number of d-orbitals at a higher energy level number of d-orbitals at a lower energy level (iii)
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9701/42 · October/November 2024 · Q4b(iv)[1]
Define the term non-degenerate d-orbitals.
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9701/42 · October/November 2024 · Q5a[1]
Complete the expression for the K stab of [Ni(en) 3 ] 2+ . K stab =
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9701/42 · October/November 2024 · Q5b(i)[1]
Predict which complex ion, [Ni(NH 3 ) 6 ] 2+ or [Ni(en) 3 ] 2+ , is present in the resulting mixture in the highest concentration. Explain your answer. complex ion present in largest concentration = (i)
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9701/42 · October/November 2024 · Q5b(ii)[1]
Complete the equation for the ligand exchange reaction occurring in (i). 2+
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9701/42 · October/November 2024 · Q5c[3]
Complete Fig. 5.1 to show the three-dimensional structures of the two isomers of [Ni(en) 3 ] 2+ . Use N N to represent the en ligand. Name the type of isomerism shown. Ni Ni Fig. 5.1
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9701/43 · October/November 2024 · Q3c(i)[1]
Iron is a transition element. Explain why iron forms stable compounds in both the +2 and the +3 oxidation states.
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9701/41 · May/June 2024 · Q2a(i)[1]
Define transition element.
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What examiners said

This was not well known. Candidates were required to state that silver can form stable ions with incomplete d orbitals. A common error was stating silver has partially filled d-orbitals and forms stable ions.
— Examiner report, February/March 2025, 9701/42 Q1(a) (Cambridge)

This was found to be a difficult question. The three nitrogen atoms in the complex can be ‘meridial’, where one N–Cr–N bond angle is 180°, or ‘facial’, where all N–Cr–N bond angles are 90°. The securest way to generate the four isomers is to draw one meridial isomer and its mirror image, and one facial isomer and its mirror image.
— Examiner report, May/June 2023, 9701/41 Q2(c) (Cambridge)

Many candidates were able to give two typical chemical properties of transition elements.
— Examiner report, May/June 2023, 9701/42 Q2(a) (Cambridge)

Practise this topic

Answer these questions online and get each one marked against the official mark scheme, with what you missed and how to fix it.

Practise chemistry of transition elements

In the syllabus

28.1 General physical and chemical properties of the first row of transition elements, titanium to

define a transition element as a d-block element which forms one or more stable ions with incomplete
sketch the shape of a 3dxy orbital and 3dz² orbital
understand that transition elements have the following properties:
explain why transition elements have variable oxidation states in terms of the similarity in energy of the 3d
explain why transition elements behave as catalysts in terms of having more than one stable oxidation
explain why transition elements form complex ions in terms of vacant d orbitals that are energetically

28.2 General characteristic chemical properties of the first set of transition elements, titanium to

describe and explain the reactions of transition elements with ligands to form complexes, including the
define the term ligand as a species that contains a lone pair of electrons that forms a dative covalent
understand and use the terms:
– and CN –
bidentate ligand including as examples 1,2-diaminoethane, en, H2NCH2CH2NH2 and the
define the term complex as a molecule or ion formed by a central metal atom / ion surrounded by one or
describe the geometry (shape and bond angles) of transition element complexes which are linear, square
(a) state what is meant by coordination number
predict the formula and charge of a complex ion, given the metal ion, its charge or oxidation state,
explain qualitatively that ligand exchange can occur, including the complexes of copper(II) ions and
predict, using E values, the feasibility of redox reactions involving transition elements and their ions
describe the reactions of, and perform calculations involving:

28.3 Colour of complexes

define and use the terms degenerate and non-degenerate d orbitals
describe the splitting of degenerate d orbitals into two non-degenerate sets of d orbitals of higher
explain why transition elements form coloured compounds in terms of the frequency of light absorbed as
describe, in qualitative terms, the effects of different ligands on Δ E, frequency of light absorbed, and
use the complexes of copper(II) ions and cobalt(II) ions with water and ammonia molecules and

28.4 Stereoisomerism in transition element complexes

describe the types of stereoisomerism shown by complexes, including those associated with bidentate
geometrical (cis/trans) isomerism, e.g. square planar such as [Pt(NH₃)₂Cl ₂] and octahedral such as
deduce the overall polarity of complexes such as those described in 28.4.1(a) and 28.4.1(b)

28.5 Stability constants, Kstab

define the stability constant, Kstab, of a complex as the equilibrium constant for the formation of the
write an expression for a Kstab of a complex ([H₂O] should not be included)
use Kstab expressions to perform calculations
describe and explain ligand exchanges in terms of Kstab values and understand that a large Kstab is due
Organic chemistry

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