Among the trihalides of nitrogen, which is the least basic ?

Options

A. `NF_3`
B. `NCl_3`
C. `NBr_3`
D. `NI_3`

Answer

To determine which trihalide of nitrogen is the least basic, we need to consider the trihalides of nitrogen, which are primarily nitrogen trichloride (NCl3), nitrogen trifluoride (NF3), and nitrogen tribromide (NBr3).

### Step-by-step Solution:

1. **Identify the Trihalides of Nitrogen**: The common trihalides of nitrogen are:
- Nitrogen trichloride (NCl3)
- Nitrogen trifluoride (NF3)
- Nitrogen tribromide (NBr3)

2. **Understand Basicity**: Basicity in this context refers to the ability of a compound to accept protons (H+ ions). The more electronegative the halogen, the less basic the nitrogen trihalide tends to be because the nitrogen atom is less able to donate its lone pair of electrons.

3. **Analyze the Electronegativity of Halogens**: The electronegativity of the halogens in the trihalides is as follows:
- Fluorine (F) > Chlorine (Cl) > Bromine (Br)

4. **Determine the Basicity of Each Trihalide**:
- **NF3**: Fluorine is highly electronegative, which makes NF3 a weak base.
- **NCl3**: Chlorine is less electronegative than fluorine, making NCl3 a stronger base than NF3.
- **NBr3**: Bromine is even less electronegative than chlorine, making NBr3 a stronger base than both NF3 and NCl3.

5. **Conclusion**: Since NF3 has the most electronegative halogen (fluorine), it is the least basic among the nitrogen trihalides.

### Final Answer:
The least basic trihalide of nitrogen is **Nitrogen trifluoride (NF3)**.