Hydration energy :

(i) Hydration energy is the enthalpy change that accompanies the dissolving of 1 mol of gaseous ions in water.

(ii) Size of ions and its charge determines extent of hydration. Greater the charge smaller the size of the ion, greater the attraction for the lone pair of O of H₂O , hence greater the extent of hydration energy.

(a) Size of the hydration ion increases.

(b) Ionic mobility decreases i.e. heavier (hydrated) ions moves slower.

Acid-base-character of oxides

(i) On moving across a period, the basic character of the oxides gradually changes first into amphoteric and finally into acidic character.

(ii) On moving down a group, reverse behavior is observed i.e., from more acidic to more basic.

(iii) Stability of oxides decreases across a period.

Hydrides

(i) Hydrogen combines with a number of other elements including metals and non-metals to form compounds called hydrides.

(ii) Covalent nature of hydrides increases across a period and decreases down the group.

(iii) Ionic hydride are better reducing agents than covalent hydride and reducing nature of hydride decreases across a period and increases down the group.