Silver halides have law solubilities in water as compared to alkali metal halides. Explain.

Explanation

Silver halides are least soluble in water though their lattice energies are almost of the same order as that of highly soluble alkali metal halides. This can be explained on the basis of the outer electronic configuration of silver ion. The electronic configuration of `Ag^(+)` is : `4d^(10)5s^(0)5p^(0)`. the electronic configuration of alkali metal ions, `Li^(+), Na^(+) or K^(+)` is `ns^(-)`. We that the d - electrons screen the nuclear charge from the outer electrons less effectively than s and p - electrons because of their poor penetration. Therefore, the effective nuclear charge, experienced by `Ag^(+)` ion is much more than effective nuclear charge in alkali metal ions. Due to greater nuclear charge, the `Ag^(+)` ion polarises the halide ion more strongely than alkali metal ion. Hence, it undergoes appreciable change from pure ionic character to covalent character. Because of the covalent character, the silver halides are less ionic and consequently their solubility in polar water is low.