Formal charge = (Number of valence electrons in neutral atom) - (Number of electrons assigned to the atom in the Lewis structure) + (Number of lone pair electrons on the atom)
For a hydrogen atom in HBr, the number of valence electrons in the neutral atom is 1. In the Lewis structure of HBr, hydrogen is bonded to bromine by a single bond, so it is assigned 1 electron. Hydrogen does not have any lone pair electrons.
Therefore, the formal charge on hydrogen atom in HBr is:
Formal charge = 1 - 1 + 0 = 0
Hence, the formal charge on hydrogen atom in HBr is 0.
