Question

Assertion :Amongst the trihalides of nitrogen, $N{F}_3,NC{l}_3,NB{r}_3$ and $N{I}_3,N{F}_3$ is least basic. Reason: In $N{F}_3$, the fluorine has the highest value of electronegativity and thus the lone pair of electrons on N-atoms is strongly bound.

Read the above assertion and reason and choose the correct option regarding it.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Assertion is incorrect but Reason is correct

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

Lewis bases need to be able to donate electrons. Fluorine is the most electronegative element in the halogens followed by chlorine, bromine and iodine.

Due to fluorine being strongly electronegative, it draws the electron density towards itself which makes it difficult for nitrogen atom to donate its lone pair of electrons. So, NF is the least basic. This trend follows the strength of electronegativity of the halides.

Since iodine is least electronegative, it is the most basic trihalide of nitrogen.

So, we have the trend, in decreasing order of basic strength:
$N{F}_3<NC{l}_3<NB{r}_3<N{I}_3$