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Physical Science, 5/e
Bill Tillery, Arizona State University

Atomic Structure

Chapter 9 Overview

Many materials used today are relatively new, created in the last few decades. These new materials are the result of modern chemical research, produced and manufactured through controlled chemical reactions. The new materials include synthetic fibers, from nylon to polyesters, and plastics, from polyethylene to Teflon. They also include water-based paints and super adhesives used in construction. The manufactured materials are lighter, stronger, and have special properties not found in natural materials. Today, such synthetic materials are used extensively in buildings, clothing, automobiles, and airplanes. The packaging, preserving, and marketing of many convenience foods are also made possible by the products of chemical research, as are manufactured vitamins and drugs that help keep you healthy. From synthetic fibers to synthetic drugs, there are millions of products today that are the direct result of chemical research.

The countless numbers of new products resulting from chemical research demonstrate understandings about matter and how it is put together. These understandings start with the most basic unit of matter, the atom. Perhaps you have wondered how incredibly tiny atoms were discovered and how they can be studied. Atoms are so tiny that they are invisible to any optical device. Even more incredible is the study of the innermost parts of these invisible atoms and the development of knowledge of how they are put together. You will soon know the answer to questions about how atoms were discovered and studied (Figure 9.1). This chapter contains the essence of the fascinating story of how the atomic concept was discovered and developed.

The development of the modern atomic model illustrates how modern scientific understanding comes from many different fields of study. For example, you will learn how studies of electricity led to the discovery that atoms have subatomic parts called electrons. The discovery of radioactivity led to the discovery of more parts, a central nucleus that contains protons and neutrons. Information from the absorption and emission of light was used to construct a model of how these parts are put together, a model resembling a miniature solar system with electrons circling the nucleus. The solar system model had initial, but limited, success and was inconsistent with other understandings about matter and energy. Modifications of this model were attempted, but none solved the problems. Then the discovery of wave properties of matter led to an entirely new model of the atom.

The atomic model will be put to use in later chapters to explain the countless varieties of matter and the changes that matter undergoes. In addition, you will learn how these changes can be manipulated to make new materials, from drugs to ceramics. In short, you will learn how understanding the atom and all the changes it undergoes not only touches your life directly but shapes and affects all parts of civilization.