Hydrogen bonds form when hydrogen atoms covalently bonded to nitrogen (N), oxygen (O), or fluorine (F) in the form of covalent compounds such as ammonia (NH
), water (H O) and hydrogen fluoride gas (HF). In these molecules, the hydrogen atoms do not pull as strongly on the shared electrons as the N, O, or F atoms. Therefore, the molecules are polar; the hydrogen atoms become positively charged and are able to form hydrogen bonds to negative ions or negatively charged parts of other molecules (such as the N, O, and F atoms that become negatively charged in these compounds). б O molecules within it are organized and interact are questions that have attracted the interest of chemists for many years.
There is probably no liquid that has received more intensive study, and there is now a huge literature on this subject. The following facts are well established: Os are located at the corners of an imaginary tetrahedron is an especially favorable (low-potential energy) configuration, but. second), so the lifetime of any specific clustered configuration will be fleetingly brief. A variety of techniques including infrared absorption, neutron scattering, and nuclear magnetic resonance have been used to probe the microscopic structure of water.
The information garnered from these experiments and from theoretical calculations has led to the development of around twenty models that attempt to explain the structure and behavior of water. More recently, computer simulations of various kinds have been employed to explore how well these models are able to predict the observed physical properties of water. This work has led to a gradual refinement of our views about the structure of liquid water, but it has not produced any definitive answer.
There are several reasons for this, but the principal one is that the very concept of structure (and of water clusters ) depends on both the time frame and volume under consideration. Thus, questions of the following kinds are still open: How do you distinguish the members of a cluster from adjacent molecules that are not in that cluster? Since individual hydrogen bonds are continually breaking and re-forming on a picosecond time scale, do water clusters have any meaningful existence over longer periods of time?
In other words, clusters are transient, whereas structure implies a molecular arrangement that is more enduring. Can we then legitimately use the term clusters in describing the structure of water? O are limited by energetic and geometric considerations, thus giving rise to a certain amount of structure within any small volume element. It is not clear, however, to what extent these structures interact as the size of the volume element is enlarged. And as mentioned above, to what extent are these structures maintained for periods longer than a few picoseconds?