Redox reaction is a chemical reaction in which the valence of elements changes before and after the reaction. This reaction can be understood as consisting of two and a half reactions, namely oxidation reaction and reduction reaction.
The essence of the reaction is that the valence has changed, that is, the electrons have shifted and moved. The semi-reaction of neutralization and valence increase, that is, electron loss, is an oxidation reaction; When the oxidation number decreases, the reaction to obtain electrons is a reduction reaction. Substances with higher valence reduce each other and are oxidized by themselves, so they are called reducing agents and their products are called oxidation products; Substance with valence oxidizes each other and is reduced by itself, so it is called oxidant, and its product is called reduction product.
What is the relationship between oxidation, reduction and valence?
1, when the element is in the lowest price state, it only has reducibility. Such as S2-, iron, etc.
When the element is in the highest valence state, it is only oxidizing. Such as Fe3+, Cu2+, KClO4, etc.
When an element is in a neutral state, it is both oxidized and reduced. Such as: Fe2+, KClO3, S+2, S+4, etc.