"Chemical Formula and Valence" Water in Nature PPT Courseware 7

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"Chemical Formula and Valence" Water in Nature PPT Courseware 7

1. What is a chemical formula?

1. The concept of chemical formula: a formula that uses element symbols and numbers to represent the composition of matter. (One substance corresponds to one chemical formula)

2. The meaning of chemical formula:

Distinguish the meaning of the number in front of the symbol and the number in the lower right corner.

The number in front of the symbol: indicates the number of particles and can be changed.

The number in the lower right corner of the symbol: indicates the number of atoms in a molecule and cannot be changed.

2. Compound price

1. Valence is used to express the number of mutual combinations between atoms.

2. How to express chemical valence

Mark the "+", "-" signs and valence directly above the element symbol.

3. Price rules

In a compound, the algebraic sum of positive and negative valencies is zero;

The chemical valence in the elemental substance is zero;

3. Application of valence

(1) According to the chemical formula, determine the valence of the element or atomic group.

Exercise 1: Indicate the valence of chlorine in each of the following substances:

KCl, Ca(ClO)2, KClO3, HClO4, Cl2, FeCl3

Exercise 2: Determine the valence of the atomic groups in the following substances:

Mg(NO3)2, BaSO4, Na3PO4, Ca(OH)2,

NH4NO3, KClO,, K2MnO4, Na2CO3

(2) Based on the valency, write the chemical formula of the compound.

Method: "Rank, mark and check"

Arrange elements Label elements Cross valence Check if algebraic sum is zero

Compound valence with positive price first

negative price last

4. Calculation of relative molecular mass

1. Calculate relative molecular mass

[Example 1]: Calculate the relative molecular mass of the following substances.

Relative molecular mass of N2 = 14× 2 = 28

Relative molecular mass of H2SO4 = 1× 2 + 32 + 16 × 4= 98

Relative molecular mass of Cu(OH)2 = 64 + (16+1) × 2 = 98

Relative molecular mass of NH4NO3 = 14+1× 4 + 14 + 16 × 3= 80

Relative molecular mass of C6H12O6 = 12× 6+ 1 ×12 + 16 × 6= 180

Challenge yourself: How to calculate the relative molecular mass of 2N2?

Class exercises

1. Which of the following symbols can correctly represent the element +3 valence aluminum ( )

(A) (B) (C) 3Al (D)

2. Among the following chemical formulas, the incorrect writing is ( )

(A) Calcium oxide (OCa) (B) Magnesium oxide (MgO)

(C) Iron trichloride (FeCl3) (D) Sulfur trioxide (SO3)

3. The pronunciation of the chemical formula Fe2O3 is ( )

(A) Iron dioxide (B) Iron dioxide (C) Iron dioxide (D) Iron dioxide (E) Iron oxide

4. The calculation formula of relative molecular mass of Mg(OH)2 is ( )

(A) 24+16+1×2 (B) 24× (16+1)×2

(C) 24×16+1×2 (D) 24+ (16+1)×2

5. The calculation formula of relative molecular mass of 2H2O is ( )

(A) 2+1×2+16 (B) 2×1×2×16

(C) 2 × (1 × 2 + 16) (D) 2 × 1 × 2 + 16

6． The relative molecular mass of H2SO4 is ________, and the mass ratio of the three elements hydrogen, sulfur, and oxygen in H2SO4 is ________.

The ratio of the number of atoms of the three elements hydrogen, sulfur, and oxygen is _______.

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"Chemical Formula and Valence" Water in Nature PPT Courseware 6:

"Chemical Formula and Valence" Water in Nature PPT Courseware 6 2. Valence In chemistry, valence is used to express the number of mutual combinations between atoms. An atomic group is a group of atoms that often acts as a whole in compounds and chemical reactions, also called roots. For convenience...

"Chemical Formula and Valence" Water in Nature PPT Courseware 5:

"Chemical Formula and Valency" Water in Nature PPT Courseware 5 1. Chemical Formula 1. Definition: A formula that uses a combination of element symbols and numbers to express the composition of a substance is called a chemical formula. For example: the chemical formula of water is H2O, the chemical formula of oxygen is O2, and the chemical formula of carbon dioxide is The chemical formula is CO..

"Chemical Formula and Valence" Water in Nature PPT Courseware 4:

"Chemical Formula and Valence" Water in Nature PPT Courseware 4 Review: What is an element? What to express? A general term for atoms of the same type with the same nuclear charge, represented by element symbols. What is the meaning of element symbols? It can represent both an element and...

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Update Time: 2024-09-09

This template belongs to Chemistry courseware People's Education Press Ninth Grade Chemistry Volume 1 industry PPT template

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