Chemistry Help: Balancing Equations

The diatomic atoms are H,O,F,Br, I,N,Cl. Can these atoms in formulas, say N+H=NH3, be more than two when left alone. Can it be something like N+H3=NH3 for balancing the equations, or can these diatomic atoms only be 2?

diatomic atoms ONLY have the subscript of two when they stand alone. hope that helps