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 the metal.
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Alfred Werner’s theory of coordination compounds, proposed in 1898, consists of several key postulates:
Dual Nature of Valency: Metals in coordination compounds exhibit two types of valences – primary (oxidation state) and secondary (coordination number).
Primary Valences: Primary valences are ionizable and satisfied by negative ions, determining the charge of the central metal ion.
Secondary Valences: Non-ionizable secondary valences are satisfied by neutral molecules or negative ions, representing the coordination number.
Spatial Arrangement: Ligands are arranged around the central metal ion in characteristic spatial configurations corresponding to different coordination numbers.
Werner’s theory laid the foundation for modern coordination chemistry, revolutionizing the understanding of metal-ligand interactions.