CHEM0030 page 1 of 6
UNIVERSITY COLLEGE LONDON
B.SC. DEGREE 2020 M.SCI. DEGREE 2020
CHEM0030: ADVANCED TOPICS IN INORGANIC CHEMISTRY
Credit value: 15
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Candidates should attempt ALL questions. Each question is marked out of 25 and the numbers in square brackets in the right-hand margin indicate the provisional allocation of marks to the subsections of a question.
[Part marks]
1. Answer ALL parts.
(a) Sketch two graphs showing the variation of radius with atomic number of (i)
lanthanide atoms and (ii) lanthanide (3+) cations. Briefly explain the similarities
and differences between the two graphs. [4]
Derive, with justification, the spectroscopic ground-state term symbol for
any Ln3+ cation excluding the middle (Gd3+) and end (La3+, Lu3+) members of the series. [4]
Give a reaction scheme for the synthesis of Sm(C5Me5)2 starting from a
(ii) State the equation for the calculation of the magnetic moment of a lanthanide cation in dilute solution. Hence determine the magnetic moment for the Ln3+ cation chosen in (i) in dilute solution given that the Landé factor gJ is given by:
gJ = 3/2 + [S(S + 1) − L(L + 1)] / [2J(J + 1)]
What assumption is made in this calculation? [4]
(iii) Discuss the application of Ln3+ cations in solid-state lasers. [3]
halide salt dissolved in an appropriate solvent. [2]
(ii) Explain why a similar synthesis of Sm(C5H5)2 is more problematic. [1]
(iii) Explain differences in reactivity of anhydrous FeCl2 with lanthanide and
actinide cyclopentadienyl compounds. [2]
(d) Madame Curie’s research work opened up the field of chemistry on the
radioactive elements. Discuss the impact of her work. [5]
2. Answer ALL parts.
(a) The catalytic cycle below shows the rhodium-catalysed hydroformylation of an
(i) Give the valence electron count and the oxidation state of Rh for compounds A to F. [6]
(ii) Explain the mechanisms of the reactions A B, B C, D E, E F
and F A. Justify your answer. [5]
(iii) Describe how the alkene ligand coordinates to the Rh centre in B. [4]
[Question 2 continued overleaf
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Question 2 continued]
(b) Describe each of the reaction types taking place in the reactions below and
identify each of the six platinum compounds G to L. [10]
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3. Answer ALL parts.
(a) Explain why, in an n-type doped semiconductor, the effective mass of the
conduction band minimum plays a large role in determining the magnitude of the
conductivity. [3]
(b) Explain how the conductivity of a metal and a semiconductor vary with
temperature. [6]
(c) The table below presents the optical band gap (Egopt,undoped), the ionization potential (IP), and the electron affinity (EA) for four direct band gap oxides A to D when undoped, and the optical band gap (Egopt,doped) when doped with 1 × 1020
cm−3 of electrons. Egopt,undoped / eV
Egopt,doped / eV IP / eV
2.8 3.2 7.6 4.8
2.0 3.0 1.3 3.2 3.1 1.6 7.2 7.0 5.6 5.2 4.0 4.3
D is most likely to be both p-type and n-type (ii) Given the equation below, which of materials A to D is likely to possess
the highest mobility for electrons? Justify your answer.
(i) Which of materials A to
dopable? Justify your answer. [2]
2 23 E 3π2n
[2] (iii) Which material would be most suited for use as a potential solar
absorber? Justify your answer. [2]
(d) Write out the equation for the dimensionless figure of merit (ZT) of a thermoelectric. Define all the terms in the equation, and explain using equations
why they are interconnected. [5]
(e) Briefly outline why the design of a high performance p-type transparent
conducting oxide remains on the “to do” list for the research community. [5]
4. Answer ALL parts.
(a) Determine the number of d-electrons and assign the nature of the principal
transition that leads to the following complexes being visibly coloured: [CrO4]3−, [CoCl4]2−, [Cu(His)2]2+, and [Au(bipy)2]+ (where His = histidine and bipy = 2,2′-bipyridyl). When charge transfer is the principal cause, indicate whether it originates from the metal or the ligand. [4]
(b) The UV-visible spectrum for a d3 octahedral complex is shown below together with the corresponding Tanabe-Sugano diagram.
(i) Assign the transitions that give rise to the two major bands in the spectrum. [4]
(ii) Using the Tanabe-Sugano diagram, calculate the position of a third band
that might be observed if the spectrum were acquired down to 200 nm. [4]
(iii) Calculate the position of at least one additional band that would be observed if the spectrum were acquired to 900 nm. Why is this transition
so weak with respect to the other transitions observed? [5]
(iv) Explain why no weak shoulders are observed in the spectrum. [2]
(c) Give two examples of how optical spectroscopy can be used to obtain information on the evolving coordination and/or oxidation state of a transition metal ion in a functional material. Propose how this information can be used to design better performing materials. [5]
END OF PAPER