* Electronegativity: Electronegativity is the ability of an atom to attract electrons in a bond. Fluorine (F) is the most electronegative element, while bromine (Br) is less electronegative. Nitrogen (N) falls somewhere in between.

* Difference in Electronegativity: The greater the difference in electronegativity between two atoms, the more polar the bond. The electronegativity difference between N and F is larger than the difference between N and Br.

In summary: The large electronegativity difference between nitrogen and fluorine creates a significant polarity in the N-F bond, making it more polar than the N-Br bond.