On every scale, water and sodium (Na+) are dependent on one another for balance. Water, sometimes referred to as the universal solvent, has the capacity to break weak bonds in other molecules. When the broken bond results in a single ion (as in the case of NaCl), water can form oriented solvent shells, meaning that each shell`s relative position in space is unchanging (one pole remains on top, the other on bottom). The shells produce electric fields that oppose the fields produced by the independent ions. As a result of orienting water around the shells, sodium weakens the hydrogen bonds of nearby water molecules. The orientation of water molecules around an ion also contributes to osmosis, the process in which water crosses through semipermeable membranes.
The solvent shell can contain between 3 and 7 water molecules, and the number can vary over time. 5 is the most common configuration. The location of water relative to Na+ falls into patterns of three molecules. This 3D model is based on the two configurations that occur most frequently. Water is shown as bright blue and sodium as darker blue.
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