Question

Which types of metals make the most efficient catalysts?

Answer 1

We know that the variable oxidation states: we already know that d block elements can take various oxidation states and these various oxidation states help them to act as a catalyst. Normally these d block elements react with the reactants and form stable intermediate and thus provide a lower energy pathway for the reaction to happen.

Complete answer:
As we know that the Transition metals form unstable intermediates with their reactants as they have a tendency to exhibit variable valency and form complexes. The unstable intermediate formed during the reaction provides an alternative path having lower activation energy for the reaction. The lowering of activation energy increases the rate of the reaction. Later these unstable intermediates decompose in order to give the final product and the catalyst is regenerated towards the end of the reaction.
Transition metal ions can also change their oxidation states and can become more effective so the Catalytic Activity of Transition Metals and their compounds are ascribed mainly to their ability of adopting variable oxidation states. The transition metals are considered to make the most efficient catalysts. This is because, when these metals are with suitable reactants, they form unstable intermediate products that can lower the activation energy and thereby making the reaction faster.

Note:
Remember that one of the properties that d block elements show is catalytic property. They act as a catalyst in many reactions. We do many reactions in organic and inorganic chemistry and there these d block elements act as a catalyst.