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

Paul Andersen explains how you can use Lewis Diagrams and VSEPR Models to make predictions about molecules. The Lewis diagrams are a two-dimensional representations of covalent bonds and the VSEPR models show how the molecule could exist in three dimensional space. [12:29]

The General Chemistry Virtual Textbook, or Chem 1, is broken into several sections covering various aspects of topics related to chemistry. This section deals with the shared-electron covalent bond and related topics such as the octet rule, electron-dot formulas, lone pair electrons, and more.

Chem4Kids looks at the 18th element in the periodic table, argon. Content focuses on argon's electrons, where you can find argon in nature and in the home, and how argon combines with other elements.

Click on the left navigation terms for some great information about the 6th element in the periodic table, "carbon." Content focuses on carbon's electrons, where you can find carbon in nature and in the home, and how carbon combines with other elements.

The 17th element in the periodic table is defined, chlorine. Find out how many electrons chlorine has and where you can find it in nature and in the home.

Here you can find some great information about the 9th element in the periodic table, "fluorine." Content focuses on fluorine's electrons, where you can find fluorine in nature and in the home, and how fluorine combines with other elements.

Here you can find lots of great information about helium. Learn about its electrons, where it exists in nature, and about the element itself!

Here you can find out about hydrogen, the first element in the periodic table. Content includes shell information, where to find it in nature, and why it is helpful to us.

Here you can find some great information about the 12th element in the periodic table, "magnesium." Content focuses on magnesium's electrons, where you can find magnesium in nature and in the home, and how magnesium combines with other elements.

Here you can find some great information about the 10th element in the periodic table, "neon." Content focuses on neon's electrons, where you can find neon in nature and in the home, and how neon combines with other elements.

Here you can find some great information about the 7th element in the periodic table, "nitrogen." Content focuses on nitrogen's electrons, where you can find nitrogen in nature and in the home, and how nitrogen combines with other elements.

Here you can find some great information about the 14th element in the periodic table, "silicon." Content focuses on silicon's electrons, where you can find silicon in nature and in the home, and how silicon combines with other elements.

Here at Chem4Kids you can find some great information about the 11th element in the periodic table, "sodium." Content focuses on sodium's electrons, where you can find sodium in nature and in the home, and how sodium combines with other elements.

Here you can find some great information about the 16th element in the periodic table, "sulfur." Content focuses on sulfur's electrons, where you can find sulfur in nature and in the home, and how sulfur combines with other elements.

This interactive activity from ChemThink takes a closer look at a covalent bond: how it is formed and how the sharing of two electrons can keep atoms together.

Electronegativity is defined and compared to electron affinity. Trends based on groups and periods are also explored. [9:54]

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