Both these elements have the same elecro negativity (3.0). But the size of nitrogen. atom (atomic radius = 75pm) is smaller than that of chlorine (atomic radius = 99pm). As a result, nitrogen atom can cause greater polarization of N – H bond than the Cl atom in Cl - H bond. Thus hydrogen bonding is present in H - H bonds (e.g., NH3) but not in a – H bonds (eg. HCl)
