1. Ionization, or ionization, refers to the process of atoms and molecules forming ions under the action of physical energy. For example, ionization can be roughly divided into two types: continuous ionization and discontinuous ionization. In classical physics, only continuous ionization can occur. Discontinuous ionization violates some physical laws and belongs to quantum ionization.
2. Easily ionized substances: strong electrolytes are electrolytes that are completely ionized into ions in aqueous solution or molten state, including strong acids, strong bases, some alkaline oxides, most salts and strong acid radicals.
3. Substances difficult to ionize: Only weak acids, bases and water are difficult to ionize. Strong bases are only potassium, sodium, barium and calcium, commonly known as the four strong bases, while others are weak bases. Only hydrochloric acid, nitric acid and sulfuric acid are strong acids, and sulfurous phosphoric acid is medium strong acid.