Catalyts - Unstable for reactions to occur?

Is it right that a catalyst needs to be in a unstable oxidation state for the reactions to occur?

If that is the case, why is it that:

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Magnesium oxide and calcium oxide, due to the fact that they are group 2 metal catalysts and have only one stable oxidation state, they are not very good catalysts for hydrogen peroxide's rate of decomposition and they do not form strong enough attachments with reactant molecules.

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having one stable oxidation state means that they are not very good catalysts. shouldn't it mean that they are not catalysts --> that they would have no effect on hydrogen peroxide's rate of decomposition?

You seem to have a lot of questions regarding catalytic mechanisms, and you don't really seem to understand how they work. You shouldn't worry about that at all I don't think, catalysts are not easy to understand. Can I ask you, what level of study you are at as I think that may help someone to give you a better answer. As with a lot of chemistry there are simple explanations, there are more complex explanations and then sometimes there are extremely complex (but accurate) explanations.

If you look back at some of my previous answers to your questions, a catalyst needs to have at least 2 stable oxidation states to facilitate the reaction. This is because the catalyst is both oxidised and reduced in the process. Those other catalysts only have 1 possible oxidation state, and so can't be oxidsed and reduced.