Transition Metal Complexes – Color, Coordination Number, and Geometry

ChemistryInorganic ChemistryAges 17–18

A beaker holds the aqua complex of a transition metal ion (Cu²⁺, Co²⁺, Ni²⁺, Fe³⁺, Cr³⁺) in its real color. Drag the ligand-concentration slider (NH₃, concentrated Cl⁻, SCN⁻, or OH⁻) so the ligand gradually replaces the water molecules in the inner coordination sphere: the solution's color shifts to that of the new complex, and a rotatable 3D model shows the correct octahedral, tetrahedral, or square-planar shape, together with the complex formula and coordination number.