Discuss the catalytic properties of transition elements.

(N/A) The transition elements and their compounds (mainly oxides) are known for their catalytic properties due to their ability to adopt multiple oxidation states and provide a large surface area.
In the first transition series,elements such as $Fe, Ni, Mn, Co$ utilize their $3d$ and $4s$ electrons to form intermediate bonds with reactant molecules on their surface. This increases the concentration of reactants on the surface and weakens the bonds in the reactant molecules,thereby decreasing the activation energy of the reaction.
Because transition elements can change their oxidation states,they act as effective catalysts by providing alternative reaction pathways.
Example: $Fe(III)$ catalyzes the reaction between iodide and persulphate ions.
$2 I^{-} + S_{2}O_{8}^{2-} \rightarrow I_{2} + 2 SO_{4}^{2-}$
The catalytic action of $Fe^{3+}$ can be shown as:
$2 Fe^{3+} + 2 I^{-} \rightarrow I_{2} + 2 Fe^{2+}$
$2 Fe^{2+} + S_{2}O_{8}^{2-} \rightarrow 2 SO_{4}^{2-} + 2 Fe^{3+}$
Other examples include $V_{2}O_{5}$ in the contact process,$Fe$ in Haber's process,$Ni$ in the hydrogenation of fats,and $TiCl_{4}$ in polymerization.
Thus,the catalytic properties of transition elements are due to the presence of vacant $d$-orbitals,the tendency to exist in variable oxidation states,and the ability to form complexes.