Structure of the Most Common Solvent, Water

Because of the repulsion of the electron pairs, the H-O-H angle is not exactly equal to the tetrahedral angle (109° 28 ), but is a few degrees less than that. 

Water molecules vibrate and rotate in the gas phase. In the liquid phase, the rotation is hindered (Ubration) because of the structure (intermolecular H bonds) and the vibrations are modified (Section 2.11.2). 

This important property of water, its tendency to form the so-called 7/with certain other atoms, is the origin of its special characteristic, the netting up of many water molecules to form large groups (Eig. 2.10). H bonds may involve other types of 

In the 1970s and 1980s, calculational approaches (in addition to the X-ray studies) were added to the tools for the attack on the structure of water. In the molecular dynamics approach, classical mechanics is used to calculate the successive movements of molecules in the structure. Such an approach is dependent on the correctness of the equation that represents the energies of interaction between the particles. The basic equation for these interactions is the Lennard-Jones 6-12 potential. 

The first term represents the attraction between two molecules and the second the repulsion that also occurs between them. 

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