When a hydrogen atom is covalently combined with an atom with greater electronegativity, the hydrogen atom will show a strong positive charge. At this time, when another atom with greater electronegativity (such as O, N, When the F atom is close to this hydrogen atom, the interaction between these two atoms is called a hydrogen bond. The hydrogen bond has saturation and directionality. Chemistry Calculation https://www.computabio.com/calculation-service-of-hydrogen-bond-and-halogen-bond.html