Skip to ContentGo to accessibility pageKeyboard shortcuts menu
OpenStax Logo
College Physics for AP® Courses

Connection for AP® Courses

College Physics for AP® CoursesConnection for AP® Courses

View of tubular arrangement of atoms, as observed with a scanning electron microscope.
Figure 30.1 Individual carbon atoms are visible in this image of a carbon nanotube made by a scanning tunneling electron microscope. (credit: Taner Yildirim, National Institute of Standards and Technology, via Wikimedia Commons)

Have you ever wondered how we know the composition of the Sun? After all, we cannot travel there to physically collect a sample due to the extreme conditions. Fortunately, our understanding of the internal structure of atoms gives us the tools to identify the elements in the Sun’s outer layers due to an atomic “fingerprint” in the Sun’s spectrum. You will learn about atoms and their substructures, as well as how these substructures determine the behavior of the atom, such as the absorption and emission of energy by electrons within an atom.

You will learn the stories of how we discovered the various properties of an atom (Essential Knowledge 1.A.4) through clever and imaginative experimentation (such as the Millikan oil drop experiment) and interpretation (such as Brownian motion). You will also learn about the probabilistic description we use to describe the nature of electrons (Essential Knowledge 7.C.1). At this scale, electrons can be thought of as discrete particles, but they also behave in a way that is consistent with a wave model of matter (Enduring Understanding 7.C). You will learn how we use the wave model to understand the energy levels in an atom (Essential Knowledge 7.C.2) and the properties of electrons.

The content in this chapter supports:

Big Idea 1 Objects and systems have properties such as mass and charge. Systems may have internal structure.

Enduring Understanding 1.A The internal structure of a system determines many properties of the system.

Essential Knowledge 1.A.4 Atoms have internal structures that determine their properties.

Essential Knowledge 1.A.5 Systems have properties determined by the properties and interactions of their constituent atomic and molecular substructures.

Enduring Understanding 1.B Electric charge is a property of an object or system that affects its interactions with other objects or systems containing charge.

Essential Knowledge 1.B.3 The smallest observed unit of charge that can be isolated is the electron charge, also known as the elementary charge.

Big Idea 5 Changes that occur as a result of interactions are constrained by conservation laws.

Enduring Understanding 5.B The energy of a system is conserved.

Essential Knowledge 5.B.8 Energy transfer occurs when photons are absorbed or emitted, for example, by atoms or nuclei.

Big Idea 7 The mathematics of probability can be used to describe the behavior of complex systems and to interpret the behavior of quantum mechanical systems.

Enduring Understanding 7.C At the quantum scale, matter is described by a wave function, which leads to a probabilistic description of the microscopic world.

Essential Knowledge 7.C.1 The probabilistic description of matter is modeled by a wave function, which can be assigned to an object and used to describe its motion and interactions. The absolute value of the wave function is related to the probability of finding a particle in some spatial region.

Essential Knowledge 7.C.2 The allowed states for an electron in an atom can be calculated from the wave model of an electron.

Essential Knowledge 7.C.4 Photon emission and absorption processes are described by probability.

Order a print copy

As an Amazon Associate we earn from qualifying purchases.


This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute OpenStax.

Attribution information
  • If you are redistributing all or part of this book in a print format, then you must include on every physical page the following attribution:
    Access for free at
  • If you are redistributing all or part of this book in a digital format, then you must include on every digital page view the following attribution:
    Access for free at
Citation information

© Mar 3, 2022 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.