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

Why do atoms react with some elements but not others, and why do they form compounds with such different properties? One of the reasons is the bonds that they form. This pathway provides resources relating to the reasons that atoms bond, and the three different types of bonds that form between atoms: covalent, ionic and metallic.

A tutorial illustrating ionic bonding. Tutorial explains how and why it occurs with animations and some interactive activities throughout. Explore the bond that forms between sodium and chlorine as you count the number of atoms present.

In this interactive activity from ChemThink, learn how ionic bonds are formed and how an ionic bond structure is represented by its formula.

In this interactive activity from ChemThink, students will learn how ionic bonds are formed and how an ionic bond structure is represented by its formula.

In this scrollable interactive, the four levels of protein folding are explored in detail by exploring the structure of hemoglobin.

Learn how to classify bonds as covalent, polar covalent or ionic by using the differences in electronegativity in this video. Video explains the Pauling scale to find the electronegativity differences in bonding. [11:38]

Khan Academy learning modules include a Community space where users can ask questions and seek help from community members. Educators should consult with their Technology administrators to determine the use of Khan Academy learning modules in their classroom. Please review materials from external sites before sharing with students.

This video/animation illustrates that a molecule as a small group of atoms stuck or bonded together with electrons. Dr. Chris Muhlstein introduces the idea of these three primary types of bonds: ionic, covalent and metallic; animations show how they form at the atomic level, and give everyday examples. [0:57]