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.
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Alfred Werner introduced the concept of primary and secondary valences in coordination chemistry. Primary valences (oxidation state) are ionizable and satisfied by negative ions, determining the charge of the central metal ion. Secondary valences (coordination number) are non-ionizable and satisfied by neutral molecules or negative ions. The coordination number represents the number of ligands directly bonded to the central metal. For example, in [Co(NH₃)₆]³⁺, cobalt (III) has a primary valence of 3 (oxidation state) and a secondary valence of 6 (coordination number), showcasing Werner’s pioneering idea that metals exhibit dual valences in coordination compounds, providing a crucial framework for understanding their structures.