JEE MainChemistryp Block Elements (Group 15, 16, 17 & 18)
Which of the following statements correctly explains the thermodynamic stability of nitrogen trihalides ( NX ₃ )?
Options
- AAll nitrogen trihalides ( NX ₃ ) are highly stable exothermic compounds due to the small size of the nitrogen
- BThe stability of nitrogen trihalides increases from F to I because the decreasing electronegativity difference
- CNF ₃ is an exothermic and stable compound because the strong N - F bond arises from effective 2 p -2 p orbital
- DNCl ₃ is the most stable nitrogen trihalide because chlorine can utilize its vacant d-orbitals for back-bondin
Correct answer
C. NF ₃ is an exothermic and stable compound because the strong N - F bond arises from effective 2 p -2 p orbital
Step-by-step solution
The stability of nitrogen trihalides depends on the strength of the N - X bond. As the size of the halogen increases from fluorine to iodine, the orbital overlap between the 2 p orbital of nitrogen and the np orbital of the halogen becomes less effective. In NF ₃ , both nitrogen and fluorine use 2 p orbitals, leading to highly effective 2 p -2 p overlap. This results in a very strong N - F bond, making NF ₃ a thermodynamically stable, exothermic compound. In contrast, NCl ₃ , NBr ₃ , and NI ₃ involve overlap betwee