Solvation

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Solvation of a sodium ion by water

Solvation or solvation found in most liquid solutions instead. It is based on an attraction or association of molecules of the solvent with molecules or ions of the solute. An interaction of the dissolved particles with the solvent leads to the stabilization of the dissolved particles in the solution. These interaction forces also lead to an orderly structure of the solvent molecules around the dissolved matter and one speaks of a solvation shell around the dissolved particles.

Solvents and Intermolecular Interactions

Solvation can in principle take place through different types of intermolecular (for ions also interatomic) interactions, such as ion-dipole, dipole-dipole, hydrogen bridge and van der Waals forces . Ion-ion interactions can occur in ionic solvents.

Particularly good solvents are polar solvents which, due to their molecular structure, have an electrical dipole . If z. B. Ions are in a polar solvent , they exert forces on the solvent dipoles due to their electrical charge . In the vicinity of positive ions ( cations ), the dipoles of the solvent usually align themselves in such a way that their negative pole is directed towards the cation and their positive pole away from the cation. In the vicinity of negative ions ( anions ) the positive pole is directed towards the anion and the negative pole away from the anion.

In the special case of water , the solvation is called hydration and the solvation shell is called the hydration shell . Since the water structure is dominated by hydrogen bonds, the structures of the hydration shells around dissolved ions are often more complex than one would expect from the simple ion-dipole interaction, as described above and shown in the figure.

An important source of information in the experimental investigation of ion solvation is nuclear magnetic relaxation , in particular the relaxation of atomic nuclei within the ions of interest.

See also

swell