How would you account for the fact that the transition metals and their compounds are found to be good catalysts in many processes?

Explanation

According to activated complex theory ( intermediate compound formation theory ), due to variable oxidation states, transition metal combines with the reactant `//`s to forma an intermediate ( an unstable species ) called activated complex whichi finally decomposes to form the products regenerating the catalyst.
`underset("Reactant")(A) + underset("catalyst")(C) rarr underset("(Intermediate)")underset("Activated complex")([AC]) rarr underset("Product")(B) + underset("Catalyst")(C)`
The reaction proceeds through a new path with lower activation energy and hence is faster.
According to adsorption theory, transition metal provides a large surface are with free valencies on which the reactants are adsorbed. As a result , the concentration of the reactants on the surface increases and hence the rate increases.