Coordination polyhedra describe the spatial arrangements of species within brackets in coordination compounds. They provide a framework for understanding the geometry around the central metal ion.

Werner’s theory, proposed in 1898, includes the concepts of primary and secondary valences. Primary valences are ionizable and satisfied by negative ions, while secondary valences are non-ionizable and correspond to the coordination number, determining the spatial arrangement of ions/groups around ...

Werner proposed that metals in coordination compounds exhibit primary and secondary valences. Primary valences are ionizable, satisfied by negative ions, while secondary valences are non-ionizable and satisfied by neutral molecules or negative ions, equal to the coordination number.

Alfred Werner was a Swiss chemist (1866-1919) who pioneered the understanding of coordination compounds. His contributions include formulating ideas about their structures and introducing the concepts of primary and secondary valences.

The lanthanoid contraction causes the radii of the third transition series elements to be very similar to those of the corresponding second series elements. The nearly identical radii of Zr (160 pm) and Hf (159 pm), resulting from the lanthanoid ...