Transition Elements | OCR A-Level Chemistry A (H432)

Transition Elements

131 questions
10 subtopics
Module 5: Physical chemistry and transition elements
Component 01 and Component 03

Ligands and complex ions, their shapes and stereoisomerism including cisplatin, ligand substitution and haemoglobin, and the coloured precipitates and redox interconversions that identify the transition metal ions..

It covers ligands, complex ions and coordination number, electron configurations from Sc to Zn, and which are transition elements, variable oxidation states, coloured ions and catalysis, the shapes of complexes, stereoisomerism and cisplatin, ligand substitution, haemoglobin and the copper complexes, hydroxide precipitates of iron, manganese and chromium, redox interconversions of iron, chromium and copper, why ligand substitution happens and the changes it causes, precipitation reactions written as aqua complexes and dissolving hydroxides in excess ammonia and distinguishing the ions.

Sample questions from Transition Elements

Answer each one closed book first, then open the answer.

Ligands, complex ions and coordination number

Is water a monodentate or bidentate ligand?

Show the answer
Monodentate.
Electron configurations from Sc to Zn, and which are transition elements

What is the electron configuration of an Fe²⁺ ion?

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1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶, or [Ar] 3d⁶: both 4s electrons are lost before any 3d electron.
Variable oxidation states, coloured ions and catalysis

Give the colours of three transition metal ions in aqueous solution.

Show the answer
Cu²⁺(aq) is pale blue, Fe²⁺(aq) is pale green and MnO₄⁻(aq) is purple.
The shapes of complexes, stereoisomerism and cisplatin

What is the shape of the tetrachlorocuprate(II) ion?

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Tetrahedral.
Ligand substitution, haemoglobin and the copper complexes

What metal ion in haemoglobin can undergo ligand substitution reactions?

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Iron.
Hydroxide precipitates of iron, manganese and chromium

Does iron(III) hydroxide dissolve in excess sodium hydroxide or excess ammonia?

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No, it does not dissolve in either.
Redox interconversions of iron, chromium and copper

What reagent and conditions can be used to oxidise chromium(III) to chromate(VI)?

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Hydrogen peroxide in hot alkaline conditions, which oxidises chromium(III) to yellow chromate(VI), CrO₄²⁻; orange dichromate(VI), Cr₂O₇²⁻, forms only on subsequent acidification.
Why ligand substitution happens and the changes it causes

What is the geometry of the [Cu(NH₃)₄(H₂O)₂]²⁺ complex?

Show the answer
Octahedral geometry is maintained.

The 10 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Ligands, complex ions and coordination number	Recall questions on monodentate and bidentate ligands, what a complex ion is, and what coordination number means.	9
Electron configurations from Sc to Zn, and which are transition elements	Recall questions on the electron configurations of scandium to zinc and their ions, the chromium and copper exceptions, the definition of a transition element, and why scandium and zinc are excluded.	15
Variable oxidation states, coloured ions and catalysis	Recall questions on the variable oxidation states and coloured ions of transition elements, colourless Sc³⁺ and Zn²⁺, and catalysis by transition metals and their compounds, from manganese(IV) oxide to industrial processes.	13
The shapes of complexes, stereoisomerism and cisplatin	Recall questions on six-fold and four-fold coordination geometries, cis-trans and optical isomerism in complexes, and how cisplatin works and its risks.	18
Ligand substitution, haemoglobin and the copper complexes	Recall questions on what ligand substitution is, oxygen and carbon monoxide at the iron centre of haemoglobin, and the copper complexes formed with ammonia and chloride.	12
Hydroxide precipitates of iron, manganese and chromium	Recall questions on the colour and identity of each precipitate with sodium hydroxide, and which dissolve in excess alkali or excess ammonia.	14
Redox interconversions of iron, chromium and copper	Recall questions on the reagents that interconvert iron(II) and iron(III) and chromium(III) and dichromate(VI), the colour changes, and the disproportionation of copper(I).	11
Why ligand substitution happens and the changes it causes	Recall questions on bond strength and stability as the drivers, and on when substitution changes the coordination number and geometry and when it does not.	16
Precipitation reactions written as aqua complexes	Recall questions on why these reactions can be written with aqua complexes, and on the two ways of writing the copper(II) ion and its hydroxide.	12
Dissolving hydroxides in excess ammonia and distinguishing the ions	Recall questions on which hydroxides dissolve in excess ammonia and which do not, the complexes formed, and using the tests to tell the ions apart.	11

Transition Elements is 131 of the 1,913 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.