In alkaline earth metal salts, the size of the metal ion is smaller and nuclear charge is higher as compared to the corresponding alkali metal ion present in the same period. Therefore, alkaline earth metal ion have a greater tendency to get hydrated and form crystalline salts whereas this tendency is negligible in alkali metal salts. For example, magnesium chloride `(MgCl_(2))` exists as `MgCl_(2).6H_(2)O` while sodium chloride (NaCl) is completely anhydrous.
