Ii. Characterizing the Microscopic Structure of Solutions Using Statistical Mechanics

When a solid is dissolved in a solvent, it might dissociate or remain intact. If the former, it becomes solvated. This means that solvent molecules will form a solvent shell or solvation shell around the solute species. The number of such nearest neighbor solvent molecules is called the coordination number. Some examples, shown as snapshots from computer simulations of solvation, illustrate the concept of coordination shells and their structures. Simulations of the aqueous solvation of the Be ion show a solvation shell that fluctuates between 6 and 4 water molecules, as the two snapshots below illustrate: The average is strongly weighted toward a coordination number of