Question

What do you understand by " hydrated ions" ? Give examples of hydrated ions and explain at least one hydrated ion's sturcture and formation.

Answer 1

Hydrated ions are ions (cations or anions) which are surrounded by water molecules. Water (H₂O) is a polar molecule. Oxygen is much more electronegative than hydrogen and therefore the shared electrons are localized more on O atom than on H atoms. Thus H atoms acquire partial positive charge and O atoms acquire partial negative charge. A molecule of water therefore act as a dipole.

When ions are present in the environment of water, than the positive ions, the cations, are attracted to the partially negative O atom, while the negative ions, the anions, are attracted to the partially positive H atom.

For example formation of hydrated ions Li ⁺ and Cl^- are shown in the image below. They are fo rmed from the LiCl crystal, which on dissolution in water breaks into its constituent ions.