Chemistry: Structure and Properties
To the Student
In this book, I tell the story of chemistry, a field of science that has not only revolutionized how we live (think of drugs designed to cure diseases or fertilizers that help feed the world), but also helps us to understand virtually everything that happens all around us all the time. The core of the story is simple: Matter is composed of particles, and the structure of those particles determines the properties of matter. Although these ideas may seem familiar to you as a 21st-century student, they were not so obvious as recently as 200 years ago. Yet, they are among the most powerful ideas in all of science. You need not look any further than the advances in biology over the last half-century to see how the particulate view of matter drives understanding. In that time, we have learned how even living things derive much of what they are from the particles (especially proteins and DNA) that compose them. I invite you to join the story as you read this book. Your part in its unfolding is yet to be determined, but I wish you the best as you start your journey.
To the Professor
In recent years, some chemistry professors have begun teaching their General Chemistry courses with what is now called an atoms-first approach.
In a practical sense, the main thrust of this approach is a reordering of topics so that atomic theory and bonding models come much earlier than in the traditional approach. A primary rationale for this approach is that students should understand the theory and framework behind the chemical “facts” they are learning. For example, in the traditional approach students learn early that magnesium atoms tend to form ions with a charge of 2+. However, they don’t understand why until much later (when they get to quantum theory). In an atoms-first approach, students learn quantum theory first and understand immediately why magnesium atoms form ions with a charge of 2+. In this way, students see chemistry as a more coherent picture and not just a jumble of disjointed facts. From my perspective, the atoms-first movement is better understood— not in terms of topic order—but in terms of emphasis.
Professors who teach with an atoms-first approach generally emphasize: (1) the particulate nature of matter; and (2) the connection between the structure of atoms and molecules and their properties (or their function). The result of this emphasis is that the topic order is rearranged to make these connections earlier, stronger, and more often than is possible with the traditional approach. Consequently, I have chosen to name this book Chemistry: Structure and Properties, and I have not included the phrase atoms-first in the title. From my perspective, the topic order grows out of the particulate emphasis, not the other way around. In addition, by making the relationship between structure and properties the emphasis of the book, I extend that emphasis beyond just the topic order in the first half of the book. For example, in the chapter on acids and bases, a more traditional approach puts the relationship between the structure of an acid and its acidity toward the end of the chapter, and many professors even skip this material. In contrast, in this book, I cover this relationship early in the chapter, and I emphasize its importance in the continuing story of structure and properties. Similarly, in the chapter on free energy and thermodynamics, a traditional approach does not put much emphasis on the relationship between molecular structure and entropy. In this book, however, I emphasize this relationship and use it to tell the overall story of entropy and its ultimate importance in determining the direction of chemical reactions. Throughout the course of writing this book and in conversations with many of my colleagues, I have also come to realize that the atomsfirst approach has some unique challenges. For example, how do you teach quantum theory and bonding (with topics like bond energies) when you have not covered thermochemistry? Or how do you find laboratory activities for the first few weeks if you have not covered chemical quantities and stoichiometry? I have sought to develop solutionsto these challenges in this book. For example, I have included a section on energy and its units in Chapter 2. This section introduces changes in energy and the concepts of exothermicity and endothermicity. These topics are therefore in place when you need them to discuss the energies of orbitals and spectroscopy in Chapter 3 and bond energies in Chapter 6. Similarly, I have introduced the mole concept in Chapter 2; this placement allows not only for a more even distribution of quantitative homework problems, but also for laboratory exercises that require the use of the mole concept. In addition, because I strongly support the efforts of my colleagues at the Examinations Institute of the American Chemical Society, and because I have sat on several committees that write the ACS General Chemistry exam, I have ordered the chapters in this book so that they can be used with those exams in their present form. The end result is a table of contents that emphasizes structure and properties, while still maintaining the overall traditional division of first- and second-semester topics. For those of you who have used my other General Chemistry book (Chemistry: A Molecular Approach), you will find that this book is a bit shorter and more focused and streamlined. I have shortened some chapters, divided others in half, and completely eliminated three chapters (Biochemistry, Chemistry of the Nonmetals, and Metals and Metallurgy). These topics are simply not being taught much in most General Chemistry courses. Chemistry: Structure and Properties is a leaner and more efficient book that fits well with current trends that emphasize depth over breadth. Nonetheless, the main features that have made Chemistry: A Molecular Approach a success continue in this book. For example, strong problem-solving pedagogy, clear and concise writing, mathematical and chemical rigor, and dynamic art are all vital components of this book.
I hope that this book supports you in your vocation of teaching students chemistry. I am increasingly convinced of the importance of our task. Please feel free to e-mail me with any questions or comments about the book.
Nivaldo J. Tro
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