The formal charge of the nitrogen atom in the molecule NH4+ can be calculated using the following formula:Formal charge = Valence electrons of the atom - Non-bonding electrons - 1/2 Bonding electrons For nitrogen in NH4+:1. Valence electrons of nitrogen = 5 as nitrogen belongs to Group 15 in the periodic table 2. Non-bonding electrons = 0 as all electrons are involved in bonding 3. Bonding electrons = 8 as there are 4 single bonds between nitrogen and hydrogen atoms, and each bond has 2 electrons Now, we can calculate the formal charge:Formal charge = 5 - 0 - 1/2 8 Formal charge = 5 - 4Formal charge = +1So, the formal charge of the nitrogen atom in the molecule NH4+ is +1.