"Quantities Represented by Element Symbols" PPT

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"Quantities Represented by Element Symbols" PPT

Part 1: Talk about the meaning of the following symbols

C

1. Represents carbon element

2. Represents a carbon atom

3. Represents carbon substances

CO2

1. Represents carbon dioxide substance

2. Indicates that carbon dioxide is composed of oxygen and carbon elements

3. Represents a carbon dioxide molecule

4. Indicates that a carbon dioxide molecule is composed of one carbon atom and two oxygen atoms.

Quantities represented by element symbols PPT, part 2 content: relative atomic mass

International regulations: relative atomic mass is used to express the mass relationship of atoms.

1. Definition of relative atomic mass

Taking 1/12 of the mass of a carbon atom as a standard, the value obtained by comparing the mass of other atoms with it is the relative atomic mass of that atom.

Referred to as atomic weight.

Why should we convert the actual mass of an atom into a relative atomic mass?

The actual mass of an atom is extremely small, making it complicated and inconvenient to calculate.

2. Steps to calculate relative atomic mass

(1) Standard:

Divide the mass of a C-12 atom into 12 equal parts, that is, one part is 1.661×10-27 kg

(2) Compare the masses of other atoms with this standard, and the resulting ratio is the relative atomic mass.

Quantities represented by element symbols PPT, Part 3 content: Thoughts and discussions

1. Is relative atomic mass the actual mass of an atom?

Can it reflect the actual mass of an atom?

Not the actual mass of the atom. is a ratio.

Energy, the greater the relative atomic mass, the greater the actual mass of the atom.

2. What are the advantages of relative atomic mass compared with the actual mass of an atom?

Numerical values ​​are relatively simple and easy to write, operate, and remember.

3. If we want to use the relative mass of an atom, do we need to calculate it?

unnecessary. The relative atomic mass of an element can be found out from the relative atomic mass table (Appendix 3).

Quantity represented by element symbol PPT, part 4 content: relative molecular mass

1. Definition

The sum of the relative atomic masses of the atoms in a molecule.

2. Calculation steps

(1) Write the correct chemical formula

(2) Find out the relative atomic mass of each element

(3) Find the sum of the relative atomic masses of each atom in the molecule

Example: Find the relative molecular masses of carbon dioxide and sulfuric acid

Known: C-12 O-16 H-1 S-32

Relative molecular mass of CO2 (carbon dioxide molecule)

Quantities represented by element symbols PPT, Part 5: Practice

1. The relative atomic mass is----( )

A. The mass of an atom

B. The value obtained by comparing the mass of an atom to 1/12 of the mass of a carbon atom

C. The value obtained by comparing 1/12 of the mass of a carbon atom with the mass of a certain atom

D. The numerical value obtained by comparing an atom to 1/12 of a carbon atom

2. It is known that the mass ratio of atoms of a certain element to carbon-12 atoms is 9, then the relative atomic mass of the element is ---- ( )

A. 108 B. 1.33

C. 108 grams D. 1.33 grams

3. Which of the following relative molecular mass calculations is correct -------- ( )

A. NO2: Relative molecular mass=14×16×2=448

B. 2NH3: Relative molecular mass = 2×14 + 1×3 = 31

C. O2: Relative molecular mass = 16×2 = 32 grams

D. 2Ca(OH)2: Relative molecular mass = 2[40+(16+1)×2] =148

Keywords: Zhejiang Education Edition eighth grade science PPT courseware for the second volume is free to download, quantities represented by element symbols PPT download, .PPT format;

For more information about the PPT courseware "Quantities Represented by Element Symbols", please click the Quantities Represented by Element Symbols ppt tag.

"Quantities Represented by Element Symbols" PPT courseware:

"Quantities Represented by Element Symbols" PPT Courseware Part One: Relative Atomic Mass International regulations: use relative atomic mass to express the mass relationship of atoms. Taking 1/12 of the mass of the carbon-12 atom as the standard, the value obtained by comparing the masses of other atoms to it,...

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Update Time: 2024-11-18

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