Give reasons for the following:
(i) Transition elements and their compounds act as catalysts.
(ii) value for
is negative whereas for
is positive.
(iii) Actinoids shows irregularities in their electronic confriguration.
(i) The different reasons as to why transition elements act as catalysts are given as follows:
(a) Due to the presence of unpaired electrons in their incomplete d - orbitals and hence possess the capacity to absorbs and re - emit wide range of energies. This makes the required energy of activation available.
(b) In number of cases the transition metal provides a suitable large surface area with free valencies on which the reactants are absorbed.
(ii) value for
is negative due to extra stability of half filled 3d- orbitals of
whereas
value for
is positive because the high energy to transform
is not balanced by low hydration energy.
(iii) The irregularities in the electronic configuration of the actinoids is due to the extra stability of the in 5-f orbitals.