The ionic compounds BaS{{O}_{4}} insoluble in water due to:

Barium sulfate (BaSO4) is an ionic compound that is insoluble in water due to its low solubility product constant (Ksp) and the nature of its constituent ions.

The solubility of an ionic compound in water is determined by the balance between the forces holding the ions together in the solid state and the forces driving the ions apart in solution. In the case of BaSO4:

Ba2+ ions: Barium ions (Ba2+) are relatively large and have a high charge density. This high charge density leads to strong electrostatic attractions between Ba2+ ions and the negatively charged sulfate ions (SO4^2-) in the solid. These attractive forces hold the Ba2+ and SO4^2- ions together tightly in the crystal lattice.

Sulfate ions: Sulfate ions (SO4^2-) are also relatively large and have a strong negative charge. They are surrounded by a shell of water molecules when dissolved in water. However, the interaction between sulfate ions and water molecules is not strong enough to overcome the strong attractions within the BaSO4 crystal lattice. As a result, the sulfate ions remain tightly bound to the barium ions in the solid and do not separate and disperse in water.

The low solubility product constant (Ksp) for BaSO4 further indicates that only a very small concentration of Ba2+ and SO4^2- ions will be present in solution at equilibrium. BaSO4 has a Ksp value of approximately 1.1 x 10^-10, which means that very few ions will dissolve in water, and most of the compound will remain in the solid form.

In summary, BaSO4 is insoluble in water due to the strong electrostatic attractions between its constituent ions (Ba2+ and SO4^2-) in the solid state and the low solubility product constant, which limits the concentration of dissolved ions in the aqueous solution.