Which of the following is least basic?

Options

A. `NF_(3)`
B. `NCl_(3)`
C. `NBr_(3)`
D. `NI_(3)`

Answer

To determine which of the given compounds is the least basic, we need to analyze the basicity of each compound based on the availability of lone pairs of electrons on the nitrogen atom and the electronegativity of the surrounding atoms.

### Step-by-Step Solution:

1. **Identify the Compounds**:
We need to consider the compounds that are being compared. Let's assume we have the following compounds:
- A: \( \text{NH}_3 \) (Ammonia)
- B: \( \text{NCl}_3 \) (Nitrogen Trichloride)
- C: \( \text{NBr}_3 \) (Nitrogen Tribromide)
- D: \( \text{NI}_3 \) (Nitrogen Triiodide)

2. **Understand Basicity**:
Basicity is related to the ability of a compound to donate a lone pair of electrons. The more available the lone pair is, the more basic the compound is.

3. **Electronegativity Consideration**:
The electronegativity of the halogens (F, Cl, Br, I) plays a crucial role. As we move down the group in the periodic table, the electronegativity decreases:
- Fluorine (F) > Chlorine (Cl) > Bromine (Br) > Iodine (I)

4. **Analyze Each Compound**:
- **Ammonia (NH3)**: Nitrogen has a lone pair that is readily available for donation. It is quite basic.
- **Nitrogen Trichloride (NCl3)**: Chlorine is more electronegative than bromine and iodine, which means it will pull the lone pair closer to itself, making it less available for donation compared to ammonia.
- **Nitrogen Tribromide (NBr3)**: Bromine is less electronegative than chlorine but more than iodine, so it will still pull the lone pair, but not as strongly as chlorine.
- **Nitrogen Triiodide (NI3)**: Iodine is the least electronegative of the halogens, meaning it pulls the lone pair the least, making it more available for donation compared to the others.

5. **Conclusion**:
Since electronegativity decreases down the group, the compound with the most electronegative substituent (NCl3) will be the least basic due to the strong pull on the lone pair of electrons. Therefore, the least basic compound among the given options is **Nitrogen Trichloride (NCl3)**.

### Final Answer:
**The least basic compound is Nitrogen Trichloride (NCl3).**

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