Biology 2e is designed to cover the scope and sequence requirements of a typical two-semester biology course for science majors. The text provides comprehensive coverage of foundational research and core biology concepts through an evolutionary lens. Biology includes rich features that engage students in scientific inquiry, highlight careers in the biological sciences, and offer everyday applications. The book also includes various types of practice and homework questions that help students understand—and apply—key concepts. The 2nd edition has been revised to incorporate clearer, more current, and more dynamic explanations, while maintaining the same organization as the first edition. Art and illustrations have been substantially improved, and the textbook features additional assessments and related resources.

By the end of this section, you will be able to do the following:

Define matter and elements
Describe the interrelationship between protons, neutrons, and electrons
Compare the ways in which electrons can be donated or shared between atoms
Explain the ways in which naturally occurring elements combine to create molecules, cells, tissues, organ systems, and organisms

A video lecture which explains the Bohr model of an atom, and explains how to create and use Bohr model diagrams to solve some practice problems. [11:51]

In the following video the wave model of the electron can be used to explain the Bohr model. Electrons are found in certain orbits because they interfere with themselves and create standing waves. When the wavelengths don't match up with a whole integer they will create destructive interference. [4:02]

As part of the General Chemistry Virtual Textbook, this site examines a list of related topics (in hyperlink format) on the atom and the Periodic Table of elements. Topics from light, particles, and waves to the Bohr model, quantum configuration, and atom structure are included.

Acting as a subtopic of the General Chemistry Virtual Textbook's section on Atoms and the Periodic Table, this site discusses Niels Bohr and his work with the atom. Topics covered in the discussion include the atom before Bohr, Bohr's orbital model, how Bohr's theory explains the hydrogen spectrum, and more.

Get a quick overview of atomic theory, from early theories to modern understanding of the atom. [1:10]

A complete, web-based, multi-media textbook covering a wide variety of Chemistry concepts.

A free CK-12 account is required to view all materials.

Learn about the Bohr model of the atom where the electrons exist in energy levels or shells. [2:50]

How did scientists figure out the structure of atoms without looking at them? Try out different models by shooting light at the atom. Check how the prediction of the model matches the experimental results.

Explore the Bohr model of atoms by studying the absorption and emission of light from simple gases in the context of starlight using this interactive simulation. A PDF worksheet and a video tutorial are also available. [2:52]

A free CK-12 account is required to view all materials.

Through a series of video lectures and some review questions, learn about the Bohr model of the atom and the periodic table of elements. [7:51]

An outstanding site that can best be described as student friendly. It describes the main differences between the classical and quantum models of the atom. Clear and well illustrated.