d-Block Elements: The d-block elements are a group of elements in the periodic table that have partially filled d-orbitals, including the transition metals as well as the inner transition metals (lanthanides and actinides).
Oxidation States:The oxidation state of an element represents the degree of oxidation of an atom, which is the number of electrons the atom has lost, gained, or shared. Transition metals can exhibit a wide range of oxidation states due to their partially filled d-orbitals.
Catalysts: Catalysts are substances that increase the rate of a chemical reaction without being consumed in the process. Many transition metals and their compounds are effective catalysts due to their ability to participate in and facilitate chemical reactions.