"Structure of Atom" The Mystery of Material Composition PPT Courseware 5

Description

"Structure of Atom" The Mystery of Material Composition PPT Courseware 5

learning target

1. Understand the structure of atoms and know the microscopic composition of atoms.

2. Understand the arrangement of electrons outside the nucleus and the formation process of ions.

3. Know the concept and calculation formula of relative atomic mass.

Modern scientific atomism (1803)

All matter is composed of the smallest indivisible particles - atoms.

Atomic model: Atoms are solid, irreducible solid balls.

Atoms are not the smallest particles that make up matter - Thomson discovered the electron (1897)

Electrons are negatively charged particles with a certain mass that are commonly found in various atoms.

Thomson's atomic model: An atom is a particle with an evenly distributed positive charge in which many electrons are embedded, neutralizing the charge, thus forming a neutral atom.

1. The composition of atoms

atomic nucleus

Proton: A proton carries one unit of positive charge

Neutron: Neutron has no charge

Electron: An electron carries one unit of negative charge

Laws in the formation of atoms

⑴Nuclear charge = number of protons = number of electrons outside the nucleus

(The number of charges carried by the nucleus is referred to as the nuclear charge)

⑵The number of protons is not necessarily equal to the number of neutrons

⑶Atoms do not necessarily contain neutrons

2. The arrangement of electrons outside the nucleus

State of motion: The electrons close to the nucleus have lower energy, and the electrons farther from the nucleus have higher energy.

Electronic layer: There are seven layers in total. The one farthest from the nucleus is called the outermost layer. The number of electrons in the outermost layer does not exceed 8 (only one layer has no more than 2 electrons).

1. Relatively stable structure: 8 electrons in the outermost layer (noble gas)

2. Generally metals: less than 4 electrons in the outermost layer

3. Generally non-metals: more than 4 electrons in the outermost shell

3. Relative atomic mass

question:

1. The mass of atoms is so small that it is extremely inconvenient to write, remember, or use. How should the mass of an atom be measured?

2. What is relative atomic mass? How does it represent the mass of an atom?

The concept 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 regarded as the relative atomic mass (Ar) of this atom.

Can we write a mathematical formula for relative atomic mass based on the definition?

Explanation: Compared with protons and neutrons, the mass of electrons is very small and usually ignored. The mass of atoms is mainly concentrated in the nucleus.

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Update Time: 2024-11-06

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