`PCI_(5)` exists but `NCI_(5)` does not because

Options

A. Nitrogen atom does not contain d-orbitals
B. `NCI_5` is unstable
C. Nitrogen atom is comparatively smaller in size
D. Nitrogen is highly inactive

Answer

To understand why PCl₅ exists while NCl₅ does not, we need to analyze the electronic configurations and the ability of these elements to form bonds. Let's break down the solution step by step.

### Step 1: Analyze the electronic configuration of phosphorus (P)
- Phosphorus has the electronic configuration: 1s² 2s² 2p⁶ 3s² 3p³.
- In the valence shell (n=3), phosphorus has 5 valence electrons (3 from 3p and 2 from 3s).

**Hint:** Look at the valence electrons to determine bonding capacity.

### Step 2: Excitation of electrons in phosphorus
- In PCl₅, phosphorus can promote one of its 3p electrons to the empty 3d orbital, allowing it to form five bonds with chlorine atoms.
- This results in the formation of five equivalent P-Cl bonds.

**Hint:** Consider the role of d-orbitals in bonding and how they can accommodate additional electrons.

### Step 3: Analyze the electronic configuration of nitrogen (N)
- Nitrogen has the electronic configuration: 1s² 2s² 2p³.
- In the valence shell (n=2), nitrogen has 5 valence electrons (2 from 2s and 3 from 2p).

**Hint:** Identify the number of valence electrons and their distribution in the orbitals.

### Step 4: Lack of d-orbitals in nitrogen
- Unlike phosphorus, nitrogen does not have d-orbitals available for electron promotion.
- Therefore, nitrogen cannot form five bonds as there is no way to accommodate additional electrons beyond the three available in the 2p orbitals.

**Hint:** Remember that the presence of d-orbitals is crucial for forming expanded octets.

### Step 5: Conclusion
- Since nitrogen cannot utilize d-orbitals for bonding, NCl₅ cannot exist, while PCl₅ can exist due to the ability of phosphorus to form five bonds through the involvement of d-orbitals.

**Final Answer:** PCl₅ exists but NCl₅ does not because nitrogen does not contain d-orbitals.

### Summary of the Answer:
- **Correct Option:** Nitrogen atom does not contain d-orbitals.