The basis for writing chemical formulas, the writing of chemical formulas

Chemical formula. Basis.

Element. Valency.

Because the chemical formula is written according to the valency of the element, I think that the valency of the element is generally four layers.

Meaning. 1 denotes a substance.

2 denotes the elemental composition of a substance.

3 denotes a molecule of a substance.

4 indicates which molecule of a substance is made of.

atoms.

It can also be abbreviated into two points, or four points in detail).

For example, H2O: 1 means water, 2 means that water is composed of two elements, hydrogen and oxygen, and 3 means one.

Water molecules. 4 means that one water molecule is made up of two.

Hydrogen atoms. And one.

Oxygen atoms. constituted.

The chemical formula is the ratio of the number of atoms in the composition of a substance.

Basis: Conservation of atoms on both sides of the chemical formula equal sign, that is, conservation of mass. Equations related to thermochemistry also require the conservation of energy on both sides of the chemical formula.

Significance: The process of microscopic chemical reaction is vividly expressed, which is conducive to practical needs. At the same time, you can intuitively see the relevant conditions of the chemical reaction, the reaction substance and so on. It is an important condition for chemistry to become a science.

The law of conservation of mass.

The atoms of the reactants are recombined to form new products (ionic equations, organic similarities).

The chemical formula is the ratio of the number of atoms in the composition of a substance.

First, write out the elemental symbols that make up the elementThen write the number of atoms that make up a single molecule in the lower right corner of the element symbol with a number.

Noble gases are directly composed of atoms and are usually represented by elemental symbols for their chemical formulas.

The structure of metal elemental and solid non-metallic elemental knots is more complex, and it is customary to use element symbols to express their chemical formulas. The writing rule of compounds is to first write out the symbols of all the elements that make up the compound in the order of positive, first and negative, and then write the number of atoms of that element in each compound molecule with a number in the lower right corner of each element symbol.

A certain order usually refers to: a compound composed of oxygen and another element, and the oxygen symbol is generally written on the right; Hydrogen and another element form a compound that forms a ridge, and the hydrogen symbol is generally written on the left; For compounds composed of metallic elements, hydrogen elements and non-metallic elements, the non-metallic element symbol should generally be written on the right. The chemical formula of a compound that is directly composed of ions is often expressed as the simplest integer ratio of its ions.

Carbon dioxide: CO2 sodium chloride: NaCl

Sodium carbonate. na2o

3 sulfuric acid: H2SO4

Carbon monoxide: CO

Chloride sub-disturbance Qiaochang iron.

FeCl2 calcium carbonate:

CaCO3 hydrochloride: HCl

Phosphorus pentoxide.

P2O5 aluminum chloride.

Alcl3 barium carbonate.

BaCO3 oxygen: O2

Ferric oxide.

Fe2O3 calcium chloride.

CaCl3 potassium carbonate.

K2CO3 nitrogen:N2

Calcium oxide. cao

Potassium chloride. kcl

Silver nitrate. AG2CO3 hydrogen:H2

Alumina: Al2O3

Ferric chloride. fecl3

Methyl iron nitrate.

fe(no3

2 chlorine: cl2

Copper oxide. cuo

Potassium sulfate. kno3

Magnesium nitrate. mg(no3)2

Zinc oxide. zno

Manganese dioxide. mno

Zinc sulfate. zaso4

Sodium hydroxide. naoh

Mercuric oxide. hgo

Sulfur dioxide. so2

Iron sulfate. fe2(so4)3

Calcium hydroxide. ca(oh)2

Magnesium oxide. mgo

Baryta. bao

Copper sulphate. cuso4

Aluminum hydroxide. al(oh)3

Ferrous oxide. feo

Sodium oxide Na2O

Barium sulfate. baso4

Magnesium hydroxide.

mg(oh)2

Silver chloride. agcl

Hydrogen peroxide H2O2

Ferrous sulfate FeSO4

Copper hydroxide. cu(oh)2

Barium chloride. bacl2

Water H2O potassium manganate.

k2mno4

Potassium permanganate. kmno4

Copper chloride. cucl2

Iron oxide. fe2o3

Potassium chlorate. kclo3

Ammonium sulphate. nh4)2so4

Calcium sulphate. caso4

Sodium sulfate. na2so4

Aluminum sulfate. al2(so4)3

Magnesium sulfate. mgso4

Silicon dioxide. sio2

Hydrogen fluoride. hf

Barium hydroxide. ba(oh)2

Iron hydroxide. fe(oh)3

Zinc hydroxide. zn(oh)2

Ferrous hydroxide.

fe(oh)2

Potassium hydroxide. koh

Barium nitrate. ba(no3)2

Ferric nitrate. fe(no3)3

Copper nitrate. cu(no3)2

Ammonium nitrate. nh4no3

Potassium nitrate. KNO3 potassium permanganate KMNO4

Zinc sulfide. zns

For the sake of my hard work, I should have given me the score.

Elemental, oxide, acid, alkali, salt chemical formula writing detailed Ling crack book macro introduction. Source Wang.

Chemical formula of the compound: (read and write in reverse order).

1) Writing steps: Write the elemental highlight symbols that make up the compound.

Metallic elements come first, and non-metallic elements come last; The positive element comes first, and the negative element comes last.

Indicate the valency of the element.

Cross (absolute).

Take the least common divisor and omit the number 1

The algebraic sum of the valence of the elements in the compound is zero.

Example: Alumina:

al o al (+3) o (-2) The number should be written on the element symbol Ten Lu Bo wide cross is that the valency of Al is the number of atoms of O, the valency of O is the number of atoms of Al, Al2O3 Check the chemical formula The algebraic sum of the valency of the elements in the compound is zero.

The chemical formula of a compound is written according to the valency, so the first thing to remember is to memorize the valency. Then write the chemical formula with valence.

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 Yuanzhou laughing pigment and write it in the lower right corner of another element as the number of atoms of the element (the offer of the fraction), 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 remembered, there is no need to standardize the valence, and the chemical formula can be written directly according to this method, which 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 by Lu Xiang in the lower right corner of k, that is, the chemical formula is obtained. ）

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).

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.

Do you understand? If you don't understand, ask me! ok!

The author clarifies one point: valency is not omnipotent, everything has its particularity, for example, sodium peroxide can not be explained with the valency knowledge you have learned now, so the knowledge of learning should be flexible, and it is necessary to grasp the general and special laws of things!