The most stable trihalide of nitrogen is :

We need to determine the most stable trihalide of nitrogen among $$NF_3$$, $$NCl_3$$, $$NBr_3$$, and $$NI_3$$.

Key factors affecting stability of nitrogen trihalides:

1. Bond strength: The N-X bond strength decreases as the size of the halogen increases:

$$N-F > N-Cl > N-Br > N-I$$

This is because nitrogen is a small atom, and it forms the strongest bond with the smallest halogen (fluorine) due to effective orbital overlap.

2. Bond energy values:

N-F bond energy $$\approx$$ 272 kJ/mol

N-Cl bond energy $$\approx$$ 200 kJ/mol

N-Br bond energy $$\approx$$ 160 kJ/mol

N-I bond energy $$\approx$$ 140 kJ/mol

3. Electronegativity effect: Fluorine is the most electronegative element. The high electronegativity of F stabilizes the N-F bond by making it strongly polar. This prevents the lone pairs on F from causing significant repulsion.

4. Trend in stability:

$$NF_3 > NCl_3 > NBr_3 > NI_3$$

In fact, $$NI_3$$ is so unstable that it is explosively sensitive when dry.

The correct answer is Option A: $$NF_3$$.