The chemical formula is derived from the valency, the valency is derived from the chemical formula,

Compounds are generally not electrical, so the charge phase + of all atoms (or clusters of atoms) is 0, and it should be kept in mind that the general atoms in the compound are usually several valences (this is to be memorized, and there is also a formula).

Potassium, sodium, silver, hydrogen (K, Na, Ag, H) +1 valence, calcium, magnesium, barium, zinc (Ca, Mg, Ba, Zn) +2 valence.

Chlorochlorobromo-iodine (F, CL, BR, I)-1 valent oxygen usually -2 valent sulfur has manganese valence.

Next, you can give it a try

hgo hg---

kmno4 mn---

naclo cl---

hclo4 cl---

There are many examples: I want to improve my chemistry scores.

Hahaha, check the correct and use the cross valence. Calculate the valency with the known valency to calculate the unknown valence, and use the law of conservation of mass to calculate the chemical formula, I am in the third year of junior high school, I have just studied it for a short time, and tomorrow I will be blessed with the physical chemistry English exam. Add.

In a compound, the algebraic sum of the valencies of all ions is always zero. That's a good calculation.

According to the algebraic sum of positive and negative valencies in the compound, it is equal to 0

Check the true or false chemical formula: according to the algebraic combination of positive and negative valencies of elements in a compound, it is 0

1) Fexo3, please calculate the value of x, and write the chemical formula:

2) Cu2(OH)2CO3, where the valency of Cu is found.

For example, propane C3H8

c is 4 valence and h is 1 valence.

A C can be connected to 4 H (like 4 hands), and an H can only be connected to Zheng Crack, and a C can be connected, so there is CH3-CH2-CH3 (simple structure), and a "-" is a hand, which is C-C-C (carbon-carbon connection) open potato.

Chemically, the valency is used to express the number of element atoms that are combined with each other, and the valency of the lead element in the element is 0(3) The basis for applying valency to derive the chemical wheel of matter is that this compound does exist.

For example, the common valency of Cl (chlorine) is -1 valence, but in Clo2 (chlorine dioxide), since the algebraic sum of the valency is zero and oxygen is -2 valence, the valency of Cl + (-2 times 2) = 0 is Cl here. To put it bluntly, the valency of a substance in the chemical formula = 0 - (the valency of another substance multiplied by the number of atoms or ions of the substance).

The memory of valency can be memorized simply by slipping through the mouth:

monovalent potassium hydrochloride, sodium silver, divalent oxygen, calcium barium, magnesium zinc;

trialuminum, tetrasilicon, pentavalent phosphorus; di-triiron, di-tetracarbon;

246 sulfur is the most common; The unit price state is always zero.

We can also directly summarize the elements with the same valency, the corresponding ions, including the atomic clusters, and strengthen the memory

Regarding the calculation of valence corresponding, there are usually three forms of calculation questions, and the basis for doing the questions is to understand Bin and keep in mind three sentences:

The valence state of elemental elements is 0;

In a compound, the algebraic sum of the valencies of all elements is 0;

In an atomic cluster, the algebraic sum of the valencies of all elements is equal to the number of charges carried by the atomic cluster, with the same sign and equal values.

Valency --- junior high school chemistry - Zhihu.

Junior Chemistry - Calculation of Valence.

Generally speaking, the valency is judged according to the number of electrons in its outermost shell, like what you are learning now should not be very deep, you only need to see how many electrons the outermost shell of the element needs to gain or lose a few electrons to become a stable structure, then it is a negative or positive valence.

Generally, if the outermost shell is greater than 4 electrons, it will gain electrons and become an 8-electron stable structure; If it is less than or equal to 4, it will lose electrons.

Like the one you have listed above, oxytic acids or oxybenates have -2 valence in the O element (a stable structure that gives 2 electrons into 8 electrons). Na, K, and H are all more active, and it is easy to lose the outermost electron and become +1 valence, NH4+ is +1 valence, 3 H shares electrons with N, and +1 valence is the valence state of the extra H shown. According to the conservation of electrons (the sum of the valencies of all elements in a molecule is 0, which is electrically neutral), we get:

The first cl: +1 valence; 2nd CL: +5 valence; s：

6 valence; n:+5 in no3(-); C: +4 valence.

In order: Fe(OH)2 (ferrous is +2 valence, it is common to have +2 or +3 valence, just remember it); Cu(Cl)2 (copper is generally +2 valence, and +1 valence, called cuprous); Fe(NO3)2 (nitrates are all -1 valent); K2mNO4 (he has one more K than potassium permanganate, where Mn is +6 valence, and Mn in potassium permanganate is +7 valence); MNO2 (MN is +4 valence). There are three common valence states of MN that are:

The method is: first memorize the valency of common elements, such as h is +1, o is -2, alkali metal +1, and so on.

The main family is equal to the number of families.

Secondly, the valency of each element in complex ions can be calculated.

so42- s+6

po43- p+5

You are talking about the valency of two elements that are known, how to write the chemical formula, right?

The valency should be memorized, and then the chemical formula should be written with the valency. Here's how to write the chemical formula with the cross method:

For example, potassium oxide: 1. Write the element symbols in order. Generally, the positive price comes first, and the negative price comes last.

2. Mark the valency of the element above the symbol of the element.

3. Cross the absolute value of the valency of the element and write it in the lower right corner of another element as the number of atoms of the element (the concession fraction that can be reduced), 4. Omit the valency as the chemical formula.

For example: potassium oxide --- ko---k

o---k2o

Calcium oxide---cao---ca2o2---cao

If the valence is well written, there is no need to mark the valency, and the chemical formula can be written directly according to this method, that is, fast and.

Accurate. For example: potassium oxide --- ko---k2o (potassium is +1 valence cross in the lower right corner of o, the number is 1 omitted and not written.) Oxygen is -2 valence and 2 is directly crossed in the lower right corner of k to get the chemical formula. ）

Another example: copper oxide --- cuo (copper + 2 valence oxygen-2 valence, can be divisible by 2, the number is 1 omitted and not written,) In this case, you can directly write the chemical formula cuo

For example, alumina ---AIO---AI2O3 (the valency is not written on paper, it is used directly in the heart).

If we encounter three elements, how do we write their chemical formulas? This involves the valency of the atomic group, and the root formula and valency of the atomic group are memorized, and then the chemical formula can also be written using the cross method. Note: When writing, it is enough to treat the cluster as an atom.

For example, sodium sulfate --- Na+1 valence, sulfate SO4 (-2) valence, so the chemical formula is: Na Ding Ding Shame Gu Yu changed to pump the whale 2SO4

Calcium nitrate---Ca(NO3)--Ca(NO3)2. If there are more than two atomic clusters, they should be enclosed in parentheses.

In this way, the chemical formula of many compounds can be written, and the valency can be memorized according to the formula, including the valency of the atomic cluster.

If it is not an atomic group, it is not required in junior high school.

If you write the chemical formula with valency, you can only write with atomic clusters in junior high school if you have more than 3 elements.

1) Fexo3, please calculate the value of x, and write the chemical formula:

2) Cu2(OH)2CO3, where the valency of Cu is found.

The chemical formula of a compound follows the law of conservation of charge, and the positively charged and negatively charged should be equal. In CO2, c is +4 valence, o is -2 valence, 2*2+4=0

For example, H2O, H is positive bivalent, and O is negative bivalent. All H positive univalent xo is negative bivalent = 0