Reaction with water
Magnesium is the least reactive of the group 2 with water and for any sort of reaction to really take place, it needs to react with steam. The reaction is as follows:
Mg + H2O ----> MgO + H2
The other elements react with cold water with increasing vigour, to produce their hydroxides:
Ba + 2H2O ----> Ba(OH)2 + H2
Solubility with hydroxides
The hydroxides of group 2 increase in solubility as we go down the group:
(hydroxides = more)
Magnesium is the least soluble. This is used in 'milk of magnesia' which helps with indigestion.
Calcium hydroxide is used with agriculture and is used to treat soil acidity.
Solubility with sulphates
The solubility of the sulphates decreases as we go down the group:
(Sulphates = less)
Magnesium is the most soluble, barium is the least.
Barium sulfate is used as a 'barium meal' to make the digestive system show up on x-rays in medicine.