Important Questions
1. What is meant by ‘lanthanoid contraction’?
2. Assign reasons for each of the following:
1. Transition metals generally form coloured compounds.
2. Manganese exhibits the highest oxidation state of +7 among the 3d series of transition elements.
3. Assign reasons for the following:
1. Copper (I) ion is not known in aqueous solution.
2. Actinoids exhibit greater range of oxidation states than lanthanoids.
4. (a) Which metal in the first transition series (3d series) exhibits + 1 oxidation state most frequently and why?
(b) Which of the following cations are coloured in aqueous solutions and why?
Sc+3, V+3, Ti+4 , Mn+2
Ti = 22, Mn = 25)
5. What are the transition elements? Write two characteristics of the transition elements.
Sample Questions
1. Why do transition elements show variable oxidation states? How is the variability in oxidation states of d-block different from that of the p-block elements?
2. How would you account for the following?
1. With the same d-orbital configuration (d4) Cr2+ is a reducing agent while Mn3+ is an oxidizing agent.
2. The actinoids exhibit a larger number of oxidation states than the corresponding members in the lanthanoid series.
3. Most of the transition metal ions exhibit characteristic in colours in aqueous solutions.
3. Explain the following observations giving an appropriate reason for each:
1. The enthalpies of atomization of transition elements are quite high.
2. There occurs much more frequent metalmetal bonding in compounds of heavy transition metals (i.e. 3rd series).
3. Mn2+ is much more resistant than Fe2+ towards oxidation.
4. How would you account for the following?
(i) Many of the transition elements are known to form interstitial compounds.
(ii) The metallic radii of the third (5d) series of transition metals are virtually the same as those of the corresponding group member of the second (4d) series.
(iii) Lanthanoids from primarily +3 ions, while the actinoids usually have higher oxidation states in their compounds, +4 or even +6 being typical.
5. How would you account for the following:
(i) Many of the transition elements and their compounds can act as good catalysts.
(ii) The metallic radii of the third (5d) series of transition elements are virtually the same as those of the corresponding members of the second series.
(iii) There is a greater range of oxidation states among the actinoids than among the lanthanoids.
