Q.Write the postulates of Werner's theory.

Step 1. Postulate 1: most elements exhibit two kinds of valence -- primary valence (in modern terms, the metal's oxidation state) and secondary valence (in modern terms, its coordination number) -- and each element tends to satisfy both simultaneously.

Step 2. Postulate 2: the primary valence of a metal ion is positive in most cases (zero in certain cases), and it is always satisfied by NEGATIVE ions.

Step 3. Postulate 3: the secondary valence is satisfied by negative ions, neutral molecules, positive ions, or a combination of these.

Step 4. Postulate 4: there are two spheres of attraction around the metal atom/ion -- an INNER sphere, the coordination sphere, whose groups are firmly attached to the metal, and an OUTER sphere, the ionisation sphere, whose groups are loosely bound and can be separated into free ions on dissolving the complex. …

List each of Werner's five postulates in order, translating 'primary valence' and 'secondary valence' into their modern equivalents (oxidati …

• Omitting the inner-sphere/outer-sphere (coordination sphere/ionisation sphere) postulate, which is the specific idea that explains WHY only some groups in a formula are ionisable. …