A model is proposed for the hydration of anions and cations based upon the influence the ions may have upon solvent polarization, and thus upon the solvent proton chemical shift parameters. Spherical cations usually form a centro-symmetric solvation shell of water molecules whose electric moments cannot interact with bulk solvent and whose proton chemical shift is, therefore, independent of temperature and is determined principally by the cation. If the cation is not spherical, and has a multipolar charge distribution (e.g., Me4N+), then the solvation shell is not centro-symmetric and the water electrical interactions are not reduced. The solvation shell chemical shift will then show normal temperature dependence, and is determined both by interaction with surrounding water and with the cation. Such a model also seems to describe the behaviour of the second hydration shell of highly charged aquo cations such as Al(H2O)3+6. In contrast, anions do not form a centro-symmetric structure, possibly because the wide separation of the hydrogen atoms in water prevents there being a unique water orientation relative to an anion, but influence water motion in the solvation shell in such a way that all electrical interactions are reduced. This, for instance, produces a small reduction in the temperature dependence of chemical shift of the water.