According to Werner's theory of coordination compounds ,

Options

A. primary valency is ionisable
B. secondary valency is ionisable
C. primary and secondary valencies are ionisable
D. neither primary nor secondary valency is ionisable .

Answer

**Step-by-Step Solution:**

1. **Understanding Werner's Theory**: According to Werner's theory of coordination compounds, every coordination compound has two types of valences: primary valence and secondary valence.

2. **Defining Primary and Secondary Valence**:
- **Primary Valence**: This is satisfied by the anions in the coordination compound. It refers to the charge balance of the compound and is ionizable.
- **Secondary Valence**: This refers to the coordination number, which is the number of ligands attached to the central metal atom. It is not ionizable and remains intact within the compound.

3. **Example for Clarity**: Consider the coordination compound [Cu(NH3)4]SO4.
- Here, the sulfate ion (SO4) acts as the anion that satisfies the primary valence. The charge on the sulfate ion is -2, indicating that the primary valency is 2.
- The ammonia (NH3) molecules are the ligands that satisfy the secondary valency. There are four NH3 molecules attached to the copper ion, indicating that the secondary valency is 4.

4. **Ionizability**:
- The primary valency is ionizable because it can dissociate in solution, leading to the formation of ions.
- The secondary valency is non-ionizable; the ligands remain coordinated to the central atom and do not dissociate under normal conditions.

5. **Conclusion**: Based on the definitions and the example provided, the correct answer to the question is that the primary valence is ionizable, while the secondary valence is not.

**Final Answer**: Primary valence is ionizable.

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