What will be the maximum valency of P with Cl?

Answer

To determine the maximum valency of phosphorus (P) with chlorine (Cl), we can follow these steps:

### Step 1: Identify the Group Numbers
Phosphorus is in Group 15 of the periodic table, and chlorine is in Group 17. This information helps us understand their bonding behavior.

**Hint:** Remember that elements in the same group often exhibit similar chemical properties.

### Step 2: Understand Electron Configuration
Phosphorus has an atomic number of 15, which gives it the electron configuration:
1s² 2s² 2p⁶ 3s² 3p³.
Chlorine, with an atomic number of 17, has the configuration:
1s² 2s² 2p⁶ 3s² 3p⁵.

**Hint:** Knowing the electron configuration helps in understanding how many electrons are available for bonding.

### Step 3: Determine Electron Needs
Chlorine needs 1 electron to complete its octet, while phosphorus needs 3 electrons to complete its octet. This indicates that phosphorus can form covalent bonds by sharing electrons.

**Hint:** Look for how many electrons each element needs to achieve a stable electron configuration.

### Step 4: Explore Bond Formation
Phosphorus can share its 3 unpaired electrons in the 3p subshell with 3 chlorine atoms, resulting in the formation of phosphorus trichloride (PCl₃). In this case, phosphorus exhibits a valency of 3.

**Hint:** Consider how many atoms of chlorine can bond with phosphorus based on its available unpaired electrons.

### Step 5: Consider Excited State Configuration
In an excited state, one of the 3s electrons can be promoted to the 3d subshell. This allows phosphorus to have 5 unpaired electrons (1 in 3s, 3 in 3p, and 1 in 3d). Thus, phosphorus can form bonds with 5 chlorine atoms, leading to the formation of phosphorus pentachloride (PCl₅). Here, phosphorus exhibits a valency of 5.

**Hint:** Think about how electron promotion can increase the number of available bonding electrons.

### Step 6: Conclusion
The maximum valency of phosphorus with chlorine is 5, as it can form PCl₅ in addition to PCl₃.

**Final Answer:** The maximum valency of phosphorus with chlorine is **5**.

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