Transition metals constitute a group of elements characterized by the filling of their outermost *d* orbitals, a property that imparts several distinctive chemical and physical characteristics. These elements frequently exhibit multiple oxidation states, allowing them to participate in diverse chemical reactions and form coordination compounds of various colors. Due to these properties, they are highly significant in catalysis, serving as vital components in industrial processes where they facilitate reactions under milder conditions. They are also critical components of natural structures and biological processes, providing essential metallic elements necessary for biochemical functions, and are widely utilized in the development of alloys and advanced materials.