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Chapter 4: Atomic Structure

Created by: CK-12

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Chapter Overview

The atom as a concept dates back to the philosophers of ancient Greece. Beginning in the later 1700s, scientific experimentation began to pave the way for a succession of models of the atom. John Dalton’s model viewed the atom as a tiny, indestructible sphere. The discovery of subatomic particles necessitated several alterations of the model. Thomson’s plum pudding model had electrons embedded within a sphere of positive charge. Rutherford’s gold foil experiment resulted in the nuclear model of the atom, where most of the mass and all of the positive charge of an atom is found in a tiny nucleus. All atoms can be described by their atomic number and their mass number. Most elements have two or more isotopes, which differ in mass because of variation in the number of neutrons in the nucleus.

Online Resources

See the following Web sites for appropriate activities:

For more information about the origins of atomic theory, from Democritus to Dalton, the following website is an excellent source: http://www.visionlearning.com/en/library/Chemistry/1/Early-Ideas-about-Matter/49

Pacing the Lessons

Lesson Class Period(s) (60 min)
4.1 Atoms 1-2
4.2 The Nuclear Model of the Atom 2
4.3 Isotopes and Atomic Mass 2

Chemistry Concepts

The table below matches each lesson from the flexbook to the Chemistry Concepts.

Flexbook Lesson Chemistry Concepts
4.1 Atoms 4.1 – 4.6
4.2 The Nuclear Model of the Atom 4.7 – 4.14
4.3 Isotopes and Atomic Mass 4.15 – 4.19

Chapter Outline

Chapter Summary

Image Attributions


Difficulty Level:

At Grade


Date Created:

Jul 25, 2014

Last Modified:

Oct 20, 2014
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