Waht Is Hydration Energy?

Hydration energy is the energy which is liberated when one mole of a substance is dissolved in excess water

Hydration energy is that energy which is released when a mole of ionic solute is added  to the
excess  of  water .

Please help me rank these ions' hydration energy

F-    
Cl-
Br-
I-
or all of them  the same?

Explain why the energy of hydration on Na+ (397 KJ/MOL) is somewhat larger than that of Cs+ (255 kJ/mol), while that of mg +2 is much larger (1908kJ/mol)??? Please help me!

Water has the ability to dissolve everything so it is used as the universal solvent. For making solutions you add water to the solute. This process is known as hydration. Energy of hydration is the amount of energy given out from an indefinite dilute solution when you add a mole of ion in a large amount of water. Simple representation of this process is
Mz+(g) + mH2O  Mz+(aq).

In the above equation Mz+(aq) is representing the number of ions which surrounds the water molecules. Secondly these are spread within the solution. For ionic compounds we have energy of hydration which has two parts. First is the amount of energy which is released when coordination compound is formed within the solution by the solvent. This energy is called Energy of Ligation. Second is the energy of dispersion when the hydrated ion or ions get spread in to the solvent medium. Enthalpy of hydration for H+ is -1130, for aluminum ion Al3+ it is -4665 and so on.

Hydration energy is the energy liberated when 1 mole of any solute is dissolved in excess water.