Catalysts at a solid surface
involve the formation of bonds between reactant molecules and atoms
of the surface of the catalyst (first row transition metals utilise 3d and
4s electrons for bonding) This has the effect of increasing the
concentration of the reactants at the catalyst surface and also weakening
of the bonds in the reacting molecules (the activation energy is lowering) Also because the transition metal ions can change their oxidation states,
they become more effective as catalysts For example, iron(III) catalyses
the reaction between iodide and persulphate ions