|
Unlimited Tutoring & Homework Help
|
|
When a H-atom is bonded to a highly electronegative atom (say, Z) by a covalent bond, the bond pair of electrons is displaced towards the electronegative atom. When solitary electron of hydrogen atom lies away from it, its nucleus gets exposed and behaves as a bare proton. Such a bare hydrogen nucleus exerts a strong electrostatic attraction on the electronegative atom of the adjacent molecule. This interaction between hydrogen atom of one molecule and the
electronegative atom of the other molecule is referred to as hydrogen bond. Thus, hydrogen bond is defined as the electrostatic force of attraction, which exists between the covalently bonded hydrogen atom of one molecule and the electronegative atom of the other molecule. The hydrogen bond is represented by dotted line (………). For e.g., in case of hydrogen fluoride the hydrogen bond exists between H atom of one molecule and fluorine atom of another molecule.
It may be noted that the hydrogen atom is acting as a bridge between the electronegative atoms of two different molecules, to one atom it is linked through a covalent bond while to the other it is linked through a hydrogen bond. However, the hydrogen atom does not lie in the centers of the two electronegative atoms because hydrogen bond and covalent bond do not have same strength. Hydrogen bond is much weaker than covalent bond and its strength ranges between 12.5 kJ mol-1 to 41.5 kJ mol-1.