Question

Which one of the following is least basic?

• A. $NF_{3}$
• B. $NCl_{3}$
• C. $NBr_{3}$
• D. $NI_{3}$

Answer 1

Answer: (A)

$NF_{3}$

Answer 2

$NF_3$ has least tendency to donate a pair of electrons (basicity) because of high electronegativity of $F$. The Lewis base strength of the other trihalides increases as the electronegativity of halogen decreases.