Maximum valency that is possible for P with Cl is _________.

Answer

To determine the maximum valency of phosphorus (P) with chlorine (Cl), we need to analyze the electronic configurations of both elements and how they can bond together.

### Step-by-Step Solution:

1. **Identify the Electronic Configuration of Phosphorus:**
- Phosphorus (atomic number 15) has the electronic configuration:
\[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^3 \]
- In the outermost shell (n=3), phosphorus has 5 electrons (2 in 3s and 3 in 3p).

2. **Identify the Electronic Configuration of Chlorine:**
- Chlorine (atomic number 17) has the electronic configuration:
\[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^5 \]
- In the outermost shell (n=3), chlorine has 7 electrons (2 in 3s and 5 in 3p).

3. **Determine the Bonding Capacity of Phosphorus:**
- Phosphorus can form bonds by using its unpaired electrons. Initially, it has 3 unpaired electrons in the 3p orbital.
- However, phosphorus can also promote one of its 3s electrons to the empty 3d orbital, allowing it to have 5 unpaired electrons available for bonding.

4. **Forming Bonds with Chlorine:**
- Chlorine can form one bond using its unpaired electron in the 3p orbital.
- Phosphorus can form 5 covalent bonds with chlorine using its 5 unpaired electrons.

5. **Coordinate Bond Formation:**
- Chlorine has 3 lone pairs of electrons. One of these lone pairs can be donated to phosphorus, forming a coordinate bond.
- This allows phosphorus to form an additional bond, bringing the total to 6.

6. **Conclusion:**
- The maximum valency of phosphorus with chlorine is 6, which can be represented as \( PCl_6 \).

### Final Answer:
The maximum valency that is possible for phosphorus with chlorine is **6**.