Solvation shell

A classic example is when water molecules arrange around a metal ion.

If the metal ion is a cation, the electronegative oxygen atom of the water molecule would be attracted electrostatically to the positive charge on the metal ion.

The result is a solvation shell of water molecules that surround the ion.

This shell can be several molecules thick, dependent upon the charge of the ion, its distribution and spatial dimensions.

This number can be determined by various methods like compressibility and NMR measurements among others.

The solvation shell number of a dissolved electrolyte can be linked to the statistical component of the activity coefficient of the electrolyte and to the ratio between the apparent molar volume of a dissolved electrolyte in a concentrated solution and the molar volume of the solvent (water):[clarification needed]

[2] The hydration layer around a protein has been found to have dynamics distinct from the bulk water to a distance of 1 nm.

[3] Solvation shell water molecules can also influence the molecular design of protein binders or inhibitors.

[4] With other solvents and solutes, varying steric and kinetic factors can also affect the solvation shell.