Editing Transition metal (section)

===Catalytic properties===
The transition metals and their compounds are known for their homogeneous and heterogeneous [[catalytic]] activity. This activity is ascribed to their ability to adopt multiple oxidation states and to form complexes. [[Vanadium]](V) oxide (in the [[contact process]]), finely divided [[iron]] (in the [[Haber process]]), and [[nickel]] (in [[Hydrogenation|catalytic hydrogenation]]) are some of the examples. Catalysts at a solid surface ([[nanomaterial-based catalyst]]s) involve the formation of bonds between reactant molecules and atoms of the surface of the catalyst (first row transition metals utilize 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 lowered). Also because the transition metal ions can change their oxidation states, they become more effective as [[Catalysis|catalysts]].

An interesting type of catalysis occurs when the products of a reaction catalyse the reaction producing more catalyst ([[autocatalysis]]). One example is the reaction of [[oxalic acid]] with acidified [[potassium permanganate]] (or manganate (VII)).<ref>{{cite journal | title = Revising the Mechanism of the Permanganate/Oxalate Reaction |vauthors=Kovacs KA, Grof P, Burai L, Riedel M | journal = J. Phys. Chem. A | doi = 10.1021/jp047061u | year = 2004 | volume = 108 | pages = 11026–11031 | issue = 50| bibcode = 2004JPCA..10811026K }}</ref> Once a little Mn<sup>2+</sup> has been produced, it can react with MnO<sub>4</sub><sup>−</sup> forming Mn<sup>3+</sup>. This then reacts with C<sub>2</sub>O<sub>4</sub><sup>−</sup> ions forming Mn<sup>2+</sup> again.