How do transition metals exhibit catalytic activity?

Explanation

Catalytic properties :
`rarr` Transition metals and their compounds form important catalysts in industry and in biological systems.
`rarr` The catalytic activity of transition metals depends on their ability to exist in different oxidation states of oxidation (or) to form coordination compounds.
Eg. : 1) `V_(2)O_(5)` is used as catalyst in manufacturing of `SO_(3)" from SO_(2)`
`2SO_(2_(g))+O_(2_(g))overset(V_(2)I_(5))hArr2SO_(3_(g))`
2) Fe is used as catalyst in manufacturing of `NH_(3)`.
`N_(2_(g))+3H_(2_(g))overset(Fe_(5))hArr2NH_(3_(g))`