Why do solubility of hydroxides of second group elements increase down the group?

When we look at factors solubility of elements there are two factors they depend on, namely:

1. Lattice energy
2. Enthalpy of hydration

So, in group II as we go down the elements have higher ionic radius and meaning high charge density. Greater charge density meaning the cation is easily able to hydrate and dissolve in water due to greater attraction with polar water molecules. (The higher charge density also means the more exothermic the hydration enthalpy)

Example: Magnesium requires steam to react vigorously as it will react very slowly with cold water. It will form its oxide and hydrogen. Strontium and Barium are more reactive than Calcium.

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Vasantha Sivaraj,

askIITians faculty