The compound which has molecular nature is gas phase but ionic in solid state is :

Options

A. `PCl_(5)`
B. `POCl_(3)`
C. `P_(4)O_(10)`
D. `PCl_(3)`

Explanation

To solve the question regarding which compound has molecular nature in the gas phase but ionic nature in the solid state, we can follow these steps:

### Step 1: Identify the Compounds
We need to analyze the given compounds. The options typically include various compounds, but for our solution, we will focus on PCl5 as indicated in the video transcript.

### Step 2: Analyze the Gas Phase Behavior
In the gas phase, we need to determine how PCl5 behaves. PCl5 is a covalent compound that exists as discrete molecules in the gas phase. This means that in the gas phase, PCl5 exhibits molecular characteristics, such as having a specific molecular structure and bonds.

**Hint:** Look for compounds that can exist as discrete molecules in the gas phase.

### Step 3: Analyze the Solid State Behavior
Next, we need to analyze how PCl5 behaves in the solid state. In the solid state, PCl5 does not remain as discrete molecules. Instead, it dissociates into ions, specifically PCl4+ and PCl6-. This indicates that in the solid state, PCl5 exhibits ionic characteristics.

**Hint:** Check if the compound can dissociate into ions when in solid form.

### Step 4: Compare with Other Compounds
We should compare PCl5 with other compounds provided in the options. Most ionic compounds will remain ionic in both solid and gas phases, while covalent compounds will remain molecular in both states. PCl5 is unique because it transitions from a molecular form in the gas phase to an ionic form in the solid state.

**Hint:** Consider the properties of other compounds to see if they show a similar transition.

### Step 5: Conclusion
Based on the analysis, we conclude that PCl5 is the compound that has molecular nature in the gas phase and ionic nature in the solid state. Therefore, the answer to the question is PCl5.

**Final Answer:** PCl5