How would you account for the following: (i) Many of the transition e

1.	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 lanthanoid
Answer» (i) The catalytic activity of transition metals is attributed to the following reasons: (a) Because of their variable oxidation states transition metals form unstable intermediate compounds and provide a new path with lower activation energy for the reaction. (b) In some cases, the transition metal provides a suitable large surface area with free vacancies on which reactants are adsorbed. (ii) This due to filling of 4f orbitals which have poor shielding effect or due to lanthanoid contraction. (iii) This is due to comparable energies of 5f, 6d and 7s orbital in actinoids.

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 lanthanoid

Answer»

(i) The catalytic activity of transition metals is attributed to the following reasons:
(a) Because of their variable oxidation states transition metals form unstable intermediate compounds and provide a new path with lower activation energy for the reaction.

(b) In some cases, the transition metal provides a suitable large surface area with free vacancies on which reactants are adsorbed.
(ii) This due to filling of 4f orbitals which have poor shielding effect or due to lanthanoid contraction.
(iii) This is due to comparable energies of 5f, 6d and 7s orbital in actinoids.

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