Question

As you have seen, lead can form the same kinds of compounds as the alkaline earth metals. Nevertheless, the solubilities may differ markedly. Give a convincing reason.

Answer 1

Solution:-

The lead compounds are more covalent in character, with a cosiderable high bond strength which means (aka lattice enthalpy).On the other hand compound is insoluble, this energy is too high for hydration enthalpies (the energy released when water surrounds an ion of either charge).

Look at the position of Pb in the periodic table and the postion of the Alkali Earth metals.

Alkali Earth Metals are in noble-gas configuration when they are doubly charged cations.
Lead however is on the right hand side, and would like to have more electrons to get converted to stablest configuration; making the bonds in lead-compounds more covalent -as well as stronger- in nature.

Insoluble compounds always have lattice enthalpies higher than the enthalpy of solvation.

Now since Alkali Earth metals like to be in ionic states; their compounds will dissolve in general more easily than the same compounds with lead, usually the lattice energy of lead compounds is much higher (In case of insoluble compounds higher than the energy that would be released upon solvation, which thus doesn't occur).

Thus we can conclude the fact of different solubilities.