Strongest Lewis Base among NBr3, NF3, NCl3, and NI3

Lewis bases are the species that donate a pair of electrons to form a covalent bond. The strength of a Lewis base depends upon the availability of electrons and the electronegativity of the central atom. The Lewis base with the highest electron density and a lower electronegativity of the central atom will be the strongest Lewis base.

NI3 is the Strongest Lewis Base

Among the given options, NI3 is the strongest Lewis base. The electronegativity of nitrogen decreases as we move down the group, and hence, the electron density around the nitrogen atom increases. This makes NI3 the strongest Lewis base among the given options.

Reasons for NI3 being the Strongest Lewis Base

1. Iodine is a larger atom than bromine, fluorine, and chlorine. Hence, it can accommodate more electron density around the nitrogen atom.

2. Iodine has a lower electronegativity than the other halogens. Therefore, the electron density around the nitrogen atom is less polarized, and it can donate the electron pair more efficiently.

3. The bond angles in NI3 are larger than in other halides. This means that the lone pair of electrons on nitrogen is less distorted and more available for donation.

Conclusion

In conclusion, the strength of a Lewis base depends on the electron density and the electronegativity of the central atom. Among the given options, NI3 is the strongest Lewis base due to the larger size and lower electronegativity of iodine, resulting in more electron density around the nitrogen atom.