Assertion : bond dissociation energy of `N-F` bond in `NF_(3)` molecule is lower than that of in `NCl_(3)` molecule.
Reason : Interelectronic repulsion exists between small size N and F atoms `N-F` bond of `NF_(3)` molecule.

Options

A. If assertion is true but the reason is false
B. If assertion is false but reason is true
C. If both assertion and reason are true and the reason is the correct explanation of assertion
D. If both assertion and reason are true and the reason is not the correct explanation of assertion

Answer

To analyze the assertion and reason provided in the question, we will break down the concepts step by step.

### Step 1: Understand the Assertion
The assertion states that the bond dissociation energy of the N-F bond in NF₃ is lower than that of the N-Cl bond in NCl₃.

**Hint:** Bond dissociation energy refers to the energy required to break a bond in a molecule.

### Step 2: Compare the Bond Lengths
In NF₃, the N-F bond is shorter than the N-Cl bond in NCl₃ because both nitrogen and fluorine are smaller atoms compared to nitrogen and chlorine.

**Hint:** Shorter bond lengths typically correlate with stronger bonds, which usually means higher bond dissociation energy.

### Step 3: Analyze Bond Strength
Since the N-F bond is shorter, it should be stronger than the N-Cl bond. Therefore, we would expect the bond dissociation energy of the N-F bond to be higher, not lower.

**Hint:** Stronger bonds have higher bond dissociation energies.

### Step 4: Consider Electronegativity
Fluorine is more electronegative than chlorine. This means that the N-F bond will have a stronger ionic character due to the greater difference in electronegativity between nitrogen and fluorine compared to nitrogen and chlorine.

**Hint:** Higher electronegativity differences lead to stronger bonds.

### Step 5: Evaluate the Reason
The reason states that inter-electronic repulsion exists between the small size of N and F atoms in the N-F bond of NF₃. While this is true, the effect of electronegativity and bond length plays a more significant role in determining bond strength.

**Hint:** Inter-electronic repulsion can weaken a bond, but it is not the only factor to consider.

### Conclusion
Based on the analysis:
- The assertion is **incorrect** because the bond dissociation energy of the N-F bond in NF₃ is actually higher than that of the N-Cl bond in NCl₃.
- The reason is **correct** in that inter-electronic repulsion exists, but it does not outweigh the factors that contribute to the strength of the N-F bond.

### Final Answer
- **Assertion:** Incorrect
- **Reason:** Correct