28.1.3—Transition elements have properties

Partially filled d subshells allow transition elements to access several oxidation states, bond to ligands in complex ions, participate in catalytic cycles and absorb visible light in many compounds.

These are linked but not identical properties: oxidation-state flexibility supports catalysis, ligand-field splitting helps explain colour, and complex formation depends on donor ligands and geometry.

Iron forms Fe²⁺/Fe³⁺, catalyses redox processes, forms [Fe(H₂O)₆]²⁺ and [Fe(SCN)]²⁺, and gives coloured compounds.

Not every d-block ion is coloured or catalytic; d⁰/d¹⁰ configurations and ligand environment matter.