Nitrogen bromide is a covalent compound, meaning it's formed by the sharing of electrons between atoms. Here's how to determine its chemical formula:

* Nitrogen (N) has a valency of 3, meaning it can form three bonds.

* Bromine (Br) has a valency of 1, meaning it can form one bond.

To satisfy their valencies, we need three bromine atoms for every nitrogen atom. Therefore, the chemical formula for nitrogen bromide is NBr₃.