Steps to write a chemical formula, how to write a chemical formula?

1. Write: According to the experimental facts** write the reactants on the left, write the chemical formula of the product on the right, and link more than one substance with a plus sign. Example:

KCLO3 - KCL O2 2, matching: balancing the chemical equation is to adjust the stoichiometric number coefficient in front of the chemical formula, so that the left and right sides of the ** atom are the same type and the number is equal, in line with the law of conservation of mass. Remember:

The number in the lower right corner of the chemical formula must not be changed, and the stoichiometric ratio in front of the assigned chemical formula should be the simplest integer ratio. Method 1: Least common multiple method Find out the least common multiple of the atom with more opportunities on the left and right sides and the number of atoms with a large change, and then adjust the number of other atoms.

Example: In KCLO3-KCL O2, first find out that the least common multiple of the number of oxygen atoms is 6, then add the coefficient 3 in front of O2, and add the coefficient 2 in front of KCLO3, so that the number of oxygen atoms in the left and right equations is equal, and then adjust the coefficient 2 in front of KCL, so that the atomic types of all elements on the left and right sides are the same, the number is equal, and the mass is also equal, which conforms to the law of conservation of mass. 2kclo3 – 2kcl 3o2 Method 2:

Parity rule: Find the element in the equation that appears more often at both ends. Whether the total number of atoms at each end of the element is an odd or even number, this element is selected as the starting point of the trim.

The coefficient that determines the other chemical formula by the introduced coefficient (adjustment) 3. Note: Indicate the reaction conditions and the state of the product, the gas is represented by the " " symbol, and the precipitated substance is represented by the " " symbol. Example:

2kclo3 - 2kcl 3o2 2NaOH CUSO4=Cu(OH)2 Na2SO4 4. Finally: change ** to an equal sign, which means that the law of conservation of mass is observed Summary: Write chemical equations in points:

Writing, matching, and annotating" in three steps.

A detailed description of the chemical formulas of element, oxide, acid, alkali and salt.

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.

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.

I'm also a person in the third year of junior high school.,I'm going to take the high school entrance examination soon.,I think zhi chemistry should be more and more familiar with it.,I'll tell you about it.。

First of all, you must know the symbols of the elements, which are of course common, and it is impossible to take the chemical formula that deviates from the book in the middle school exam.

1.Noble gases and metals: directly composed of atoms such as Cu, He

2.Partial solid non-metals: Because of the complex structure, element symbols such as: c, s, p

3.Diatomic molecules: H2, etc.

4.The order in which the elements are arranged in a chemical formula.

1) In compounds composed of metals and non-metals, the metal elements are written on the left and the non-metallic elements are written on the right, such as: KCI

2) In compounds with non-metallic composition at the same time, the positive valence element is written on the left, and the negative valence element is written on the right, such as: HCI

3) In oxides, the symbol of the oxygen element is written on the right, and the element on the other side is written on the left, such as: co

Anyway, remember this mantra.

Metallic left, non-metallic right; The positive price is left, and the negative price is right; Oxygen in oxides comes last.

This is written by the puppet himself, absolutely original.

A detailed description of the chemical formulas of element, oxide, acid, alkali and salt.

Listen attentively in class, and the chemical formula can still be written, which proves that you didn't listen well in class.

Here's what our teachers taught us::

Potassium, sodium, silver, hydrogen +1 valence.

Calcium, magnesium, barium, zinc, zhidao, copper +2 valence.

CFO-iodine-1 valence.

Carbon has an inner +2 and a +4

Iron has +2 and +3

Oxygen has -2 valence, and aluminum has +3 valence.

Silicon has +4 valence and phosphorus has +5 valence.

Sulfur has +2, +4 and +6

Nitrogen has -3, +2, +4 and +5

What I summarized on the basis of the teacher may be simpler: potassium, sodium, silver, hydrogen + 1 valence.

Calcium, magnesium, barium, zinc, copper(+)2 valence.

CFO-iodine-1 valence.

Carbon has +2 and +4

Iron has +2 and +3

Aluminum, silicon, phosphorus (respectively).

Sulfur has +2, +4, and +6

Oxygen has -2 valence.

Nitrogen has -3, +2, +4 and +5

The brackets in parentheses can not be memorized, just know for yourself)