Why the water solubility of Sulfates decrease when moving down the Group IIA?

as you move down the group the size of ion increase, charge remains same so charge density decreases. As charge density decreases the solvation energy decreases. So the total energy released on the solvation of ion is less as u move down the group. But there is another factor of bond strength. as u move down the group bond strength also decreases. so the difference between solvation energy and energy required to break the bond i.e total solvation energy may increase. therefore you may find exceptions to the trend. mark this as best answer if u r satisfied.