Topic overview

Start with the big picture

D-block metals span groups 3–12 and periods 4–7. Their (n–1)d and ns orbitals are close in energy, helping explain features such as variable oxidation states and, when d orbitals are partly filled, colored compounds. Many show strong electrical and thermal conductivity, form coordination complexes with ligands, and participate in catalytic processes. The term “transition metal” is often used more narrowly: elements such as Zn, Cd, and Hg belong to the d-block but are commonly excluded from that subset because of their filled d subshells in common oxidation states. This introduction establishes the periodic-table position and classification of d-block metals before exploring how electronic structure relates to their properties and chemical behavior.