It is the change in valence state of a substance when a redox reaction occurs
1. The following is about valence (two short poems)
Positive Valence Song< /p>
Potassium monohydrogen, sodium ammonia silver,
Dicalcium, magnesium, barium and zinc,
Copper one or two, iron two or three,
Three aluminum, four silicon, two and four carbon.
Negative valence song
Negative hydroxide, nitrate, fluoride, chlorobromide,
Negative disulfate, carbonate, oxygen and sulfur,
< p>Negative trinitrogen changes the price of chlorine, phosphorus, sulfur, manganese and carbon,Roots and non-metals are mostly seen in negative prices.
Chlorine, manganese, sulfur, nitrogen, and phosphorus, these elements have three or four valences and can be recorded separately. Also note that the valence of all elements in the element is 0. The rest will be remembered based on the two poems above. The two poems were taught to us by our junior high school chemistry teacher. I personally find them particularly useful, especially the "Regular Price Song".