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IGNOU MCH-11 (July 2025 – June 2026) Assignment Questions
1. a) Explain the trends of ionization energy down the groups of the elements in the periodic table. How are the higher values of ionisation energies of the 5d transition elements justified?
b) What is the trend of the stability of the +6 state for Group 6 elements like tungsten, molybdenum and chromium? Which other group show a similar trend? Justify your answer.
2. a) Explain the structure of the pentafluorotellurate(IV) anion with the help of VSEPR theory. What is the point group of the symmetry in it?
b) With suitable illustration explain the theory of Dewar for π bonding in phosphazenes. What is phospham and how it is synthesized? Give suitable reaction.
3. a) Give the classification of nonclassically bonded organometallic compounds.
b) With any two suitable examples show how organanometallic complexes of different classes may be stabilized by bulky ligands.
4. a) With suitable illustration explain the bent tin-tin double bond in (SnR2)2; where R = (Me3Si)2CH.
b) With the help of suitable examples and structures, explain why some of the 16-electron organometallic complexes are stable. For a d metal ion which form will be more stable, 16-electron square planar complex (d and 8 ligand electrons) or a 18-electron complex (d8 and 10 ligand electrons)? Justify your answer.
5. a) With suitable diagrams explain the electronic structure of NO and its binding to a metal fragment on the covalent model.
b) Compare the characteristics of electron-rich phosphines with those of electron poor phosphines regarding their σ donor and π acceptor capacities. What happens to these characteristics when the average electronegativity of the three groups attached to P increases?
6. a) Explain the π system of the allyl group with the help of molecular orbital theory. Illustrate your answer.
b) Give the structure of titanocene with its IUPAC nomenclature. How is the Hund’s rule obeyedn in manganocene?
7. a) Give the reactions for preparation of decaborane(14) from B5H8- anion. Which is the only neutral dodecaborane and how is it prepared? Give suitable equation.
b) Explain the structure of Mo6Cl8 2- . Which are the two main classes of metal atom cluster compounds?
8. a) Give the electronic configuration of d and d complexes in both weak and strong fields. Also calculate their CFSE.
b) Explain the structure of normal spinels with a suitable example. Give suitable illustration.
9. a) Give suitable equations and explain the orbital and spin contributions towards paramagnetism in a complex.
b) What is the expected magnetic moment of the complex MnF3? What sort of stereochemistry is seen in it? What is the electron configuration in it based on crystal field theory.
10. a) Write the Russell-Saunders terms symbols for states with the angular momentum quantum numbers (L,S) (a) (1, 1/2) (b) (2,1) (c) (0, 3/2) (d) (3, 0).
b) Explain how the R- and S- labels are used for enantiomers. Explain the λ and δ conformations of methyl axial and methyl equatorial respectively. Give suitable illustrations for all of these.
IGNOU MCH-11 (January 2025 – December 2025) Assignment Questions
1. a) Give the trends in metallic radii of alkali, alkaline earth and transition metals of fourth, fifth and sixth periods with proper illustration.
b) Explain periodic variation of electronegativity with atomic number for the first six rows of the periodic table.
2. a) What are the possible molecular structures of xenon hexafluoride? Explain with suitable figures. Explain the geometrical isomers of Ma2b2cd complex with suitable figures.
b) With suitable illustration explain the theory of Craig and Paddock for π bonding in phosphazenes. Give some synthetic routes for polyphosphazenes.
3. a) Explain the concept of hapticity giving suitable examples.
b) What is β-elimination in organometallic chemistry? What is the role of agnostic alkyls in β-elimination?
4. a) With suitable examples explain fluxional organometallic compounds. What are the probable of symmetric and semibridging carbonyls. Give suitable examples.
b) Determine the number and symmetry designations of the infrared-active C-O modes in the following derivatives of Mo(CO)6.
Mo(CO)5PR3 cis-Mo(CO)4 (PR3)2
trans-MO(CO)4 (PR3)2 fac-Mo(CO)3 (PR3)3
5. a) With the help of molecular orbital theory explain the geometry of the nitrosyl ligand.
b) What are the polydentate phosphines? How do you prepare molybdenocene.
6. a) Give the structures of 
b) What are Wade’s Rule? Apply them to any metalloborane.
7. a) Explain the different types of compounds having multiple metal-metal bonds.
b) If pairing energy P for Fe3+ ion is 29,875 cm-1 and ∆O for [Fe (H2O)6]3+ is 13,700 cm-1, find out
(i) whether the complex is high spin or low spin
(ii) the number of unpaired electrons
(iii) whether the complex is coloured or not?
8. a) Give the octahedral as well as tetrahedral field electronic configuration for Cr3+ and Co3+ ions. Which site will be preferred by these ions, octahedral or tetrahedral? Justify your answer.
b) Explain the Curie Law and Curie-Weiss Law along with their plots.
9. a) With suitable illustration explain the super exchange mechanism in d-metal complexes.
b) Write the Russell-Saunders terms symbols for states with the angular momentum quantum numbers 
10. a) [FeF6]3- is almost colourless whereas [CoF6]3- is coloured and exhibits only a single band in the visible region of the spectrum. Justify.
b) Explain charge transfer spectra with suitable examples. What is the reason for the deep purple colour of the permanganate ion?
