Hydration energy is the amount of energy released when one mole of ions undergo hydration . The more the ion is hydrated, the more heat is released. the following table is the trend of Heat of Hydration [hydration enthalpy] in Halogens. read more
The trend seen for the complete removal of an electron from the gaseous halogen atoms is that fluorine has the highest IE 1 and iodine the lowest. To overcome the attractive force of the nucleus means that energy is required so that the Ionisation Energies are all positive. read more