According to the classical acid-base theory and Lewis acid-base theory, there are two kinds of acidic substances:
In the first category, the classical acid-base theory holds that substances that can provide hydrogen protons are called acids (Br? Nsted acid), also known as protonic acid, such as hydrochloric acid and sulfuric acid (HCl).
In the second category, Lewis acid-base theory holds that substances that can accept an electron pair are called acids (Lewis acids), such as cerium trichloride, ferric chloride and magnesium chloride.
Extended data
The discovery background of acidic substances:
Arrhenius, a Swedish scientist, summarized a lot of facts in 1887 and put forward the essential viewpoint of acid-base ionization theory. In the theory of acid-base ionization, the definition of acid-base is: any substance in which all cations ionized in aqueous solution are hydrogen ions is called acid;
A substance whose ionized anions are all hydroxide ions is called alkali, and the essence of acid-base reaction is the reaction that hydrogen ions combine with hydroxide ions to form water.
Limitations: In the absence of water, acid-base reactions can also occur, for example, hydrogen chloride gas reacts with ammonia to produce ammonium chloride, but these substances are not ionized, and ionization theory cannot discuss such reactions. To solve these problems, the concept of acid-base must exist independently without solvent. At the same time, the concept of acid-base cannot exist in isolation without chemical reaction, and acid and base are interdependent and relative.
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