The bond in NBr3 (Nitrogen tribromide) is classified as covalent. In this molecule, nitrogen (N) and bromine (Br) share electrons to form covalent bonds. However, because nitrogen is less electronegative than bromine, the shared electrons are not distributed equally. This leads to a polar covalent bond.
To elaborate, electronegativity is the measure of an atom’s ability to attract electrons in a bond. Nitrogen has an electronegativity of about 3.0, while bromine has an electronegativity of about 2.8. The slight difference in electronegativity causes bromine to pull the shared electrons slightly closer to itself, creating a dipole moment in the molecule. Thus, the N-Br bonds are considered polar covalent bonds.
In summary, the bond in NBr3 is covalent and polar due to the difference in electronegativity between nitrogen and bromine.