The eighth edition of Chemistry continues the tradition of providing a firm foundation in chemical concepts and principles while presenting a broad range of topics in a clear, concise manner. My aims are to strike a balance between theory and application by incorporating real examples and to help students visualize the three-dimensional atomic and molecular structures that are the basis of chemical activity. An integral part of the text is to develop students' problem-solving and critical thinking skills.

Recent editions of Chemistry have witnessed the rapid advances in technology. While the textbook is still the best medium for students to use as they learn new concepts in chemistry, we employ many tools technology has to offer to help students visualize chemistry and explore ideas in an interactive environment. The integration of these tools in this textbook serves to inspire the students in their learning process, and takes them beyond the confines of the traditional textbook.

Organization
The emphasis in this edition is on clarification. I have tried to go through all processes in a step-by-step manner. You will find this style within the text of each chapter and also in the worked examples. I have reviewed and revised chapters based on the comments from reviewers and users. Some examples are shown below:
• Improved the treatment of limiting reagent (Section 3.9).
• Provided clearer explanation of atmospheric pressure (Section 5.2).
• Completely reorganized Chapter 6 so the topics flow in a more logical manner. In addition, the units for enthalpy change for chemical reactions (∆H) are now given in kJ/mol. The same per mole unit is used for changes in entropy (∆S) and Gibbs free energy (∆G) in Chapter 18. As a result, the units are consistent in important thermodynamic equations such as Equation (18.14).
• Used radial probability plots to explain the shielding effect in Chapter 7.
• Clarified the influence of temperature on a reacting system at equilibriumin Chapter 14.
• Improved the treatment of acid strength that now includes carboxylic acids in Chapter 15.
• Substantially revised the discussion of entropy and Gibbs free energy in Chapter 18.
• Added many new end-of-chapter problems and revised a number of others. As in previous editions, there is a good mix of easy, intermediate, and more challenging problems.
• Added two new Chemical Mysteries in Chapters 1 and 24.

Art
A completely new design can be seen throughout the eighth edition. As always, I strive for a clean but visual design. Each chapter opens with a two-page spread containing a photo with accompanying molecular models to illustrate the chemical or physical process at the molecular level.

Many of the line art drawings have a new look while still maintaining accurate chemical information.

Molecular art, created by the Spartan drawing program, is an asset I cannot resist using to emphasize molecular geometry. In this edition, I have expanded the use of electrostatic potential maps that show charge distribution in molecules according to the colors of the rainbow (red through blue tracks regions of greater negative charge to greater positive charge). An example is the electrostatic potential map of hydrogen fluoride shown in Figure 9.4. These diagrams help students better understand polarity of molecules, intermolecular forces, acid and base properties, and reaction mechanism.

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I have also added new molecular art to line drawings and photos and to a number of end-of-chapter problems. In addition, we have updated the photo program to complement the visual layout of the design.

Pedagogy
The development of problem-solving skills has always been a major objective of this text. Almost all of the Worked Examples in the eighth edition have been substantially revised. I have added a strategy step after stating the problem, followed by a step-by-step solution process, and then a check requesting the student to look at the answer to see if it makes sense. Additionally, marginal references enable students to apply new skills to other, similar problems at the end of the chapter. Each Worked Example is followed by a Practice Exercise which asks the students to solve a similar problem on their own. The answers to the Practice Exercises are provided after the end-of-chapter problems in each chapter.

As an instructor, I often tell my students that a good learning tool is to sketch out the inner workings of a problem. In some of the Worked Examples, I have included this type of drawing (for example, see Example 6.1 on p. 222). It is what a scientist would do as he/she works out a problem (sometimes called the back-of-the-envelop calculations).

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Inside the front cover of this text you will see a periodic table. I have added the names of the elements under the symbols to this table. This format makes it convenient to have the relevant information all at the same location.

Index to Important Figures and Tables
The back inside cover shows a list of important figures and tables with page references. This index makes it convenient to quickly look up information when a student is solving problems or studying related subjects in different chapters.