Werner's Theory (Primary vs. Secondary Valency)

Core Principles:

$$\begin{aligned} \text{Primary Valency} &\implies \text{Oxidation State (Ionizable / Non-directional)} \\ \text{Secondary Valency} &\implies \text{Coordination Number (Non-ionizable / Directional)} \end{aligned}$$

Notation:

• $$\text{Primary valency}$$ satisfies ionic charges with negative ions;
• $$\text{Secondary valency}$$ satisfies spatial coordination geometry using neutral or negative donor ligands.