Basically, the valence of most elements and their positive and negative valence need to be mastered by memory.

Monovalent potassium sodium hydrogen chloride silver, bivalent barium calcium magnesium zinc oxide;

The valence of aluminum, carbon, sulfur, negative divalent, nitrogen and phosphorus is three to five;

Iron can be changed into bivalent and trivalent, and copper and mercury can be seen in bivalent and bivalent;

It is necessary to distinguish between positive and negative valence changes. Don't forget that a single substance is zero Note that chlorine is generally-1, but it can also be+1, +3, +5, +7, and oxygen is -2.

Extended data:

Potassium, sodium, silver and hydrogen are monovalent, and barium, zinc, calcium and magnesium are monovalent.

One, two, one, two, three iron and cuprous ferrous are low in price,

Aluminum is n-trioxane and negative two, and chlorine is negative one, which is the most common.

Sulfur has negative two positive four six, positive two positive three iron transformation,

Twenty-three irons, twenty-four carbons, and zero-valent elements will never change.

Keywords hydroxyl mononitrate, carbonic acid disulfate,

Negative three records of phosphate, positive one record of ammonium,

Other elements have variable prices and are calculated alive after death.

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