In solid state, `PCl_(5)` is a……..

Options

A. covalent solid
B. octahedral structure
C. ionic solid with `[PCl_(6)]^(+)` octahedral and `[PCl_(4)]^(-)` tetrahedral
D. ionic solid with `[PCl_(4)]^(+)` tetrahedral and `[PCl_(6)]^(-)` octahedral

Answer

To solve the question "In solid state, PCl₅ is a…", we need to analyze the structure and behavior of phosphorus pentachloride (PCl₅) in its solid form.

### Step-by-Step Solution:

1. **Understanding PCl₅ Structure**:
- PCl₅ consists of one phosphorus atom bonded to five chlorine atoms. In the gaseous state, it has a trigonal bipyramidal geometry.

2. **Solid State Behavior**:
- In the solid state, PCl₅ does not remain as a simple molecular compound. Instead, it undergoes ionization.

3. **Ionization in Solid State**:
- In the solid state, PCl₅ can dissociate into two ions:
- PCl₄⁺ (tetrahedral)
- PCl₆⁻ (octahedral).
- This means that in the solid state, PCl₅ exists as a combination of these two ionic species.

4. **Charge Distribution**:
- The phosphorus atom in PCl₅ can lose one electron to form PCl₄⁺, which has a positive charge and is surrounded by four chlorine atoms in a tetrahedral arrangement.
- Conversely, if phosphorus gains an electron, it forms PCl₆⁻, which has a negative charge and is surrounded by six chlorine atoms in an octahedral arrangement.

5. **Conclusion**:
- Therefore, in the solid state, PCl₅ can be represented as PCl₄⁺ and PCl₆⁻, indicating that it exists as a salt-like structure in solid form.

### Final Answer:
In solid state, PCl₅ is a mixture of PCl₄⁺ (tetrahedral) and PCl₆⁻ (octahedral).

---