Subatomic particles Atomic structure

Dalton pictured atoms as featureless spheres, like billiard balls. Today, we know that atoms have an internal structure they are built from even smaller subatomic particles. In this book, we deal with the three major subatomic particles the electron, the proton, and the neutron. By investigating the internal structure of atoms, we can come to see how one element differs from another and see how their properties are related to the structures of their atoms. 

The earliest experimental evidence for the internal structure of atoms was the discovery in 1897 of the first subatomic particle, the electron. The British physicist... 

Chemical advances frequently are driven by technology. The discovery that atoms have inner structure was an outgrowth of the technology for working with radioactive materials. In Chapter 2 we describe a famous experiment in which the structure of atoms was studied by bombarding a thin gold foil with subatomic particles. A contemporary example is the use of lasers to study the details of chemical reactions. We introduce these ideas in Chapters 7 and 8. 

From 50 years to 100 years after Dalton proposed his theory, various discoveries showed that the atom is not indivisible, but really is composed of parts. Natural radioactivity and the interaction of electricity with matter are two different types of evidence for this subatomic structure. The most important subatomic particles are listed in Table 3-2, along with their most important properties. The protons and neutrons occur in a very tiny nucleus (plural, nuclei). The electrons occur outside the nucleus. 

The internal structure of the atom, that is, how the subatomic particles are arranged in space within the atom, is very complicated. All the protons, plus varying numbers of electrically neutral particles called neutrons, cluster inside the central nucleus. The 1... 

When Mendeleev invented the periodic table, he was well-acquainted with Dalton s atomic theory. He knew nothing, however, about subatomic particles, and especially the electron, which is the foundation for the modern periodic table s distinctive shape. Because the original periodic table developed out of experimental observations, chemists did not need an understanding of atomic structure to develop it. (As you will see in section 3.3, however, the periodic table easily accommodates details about atomic structure. In fact, you will learn that the modern periodic table s distinctive design is a natural consequence of atomic structure.)... 

The first sections of this reference book set the stage for the presentation of the elements. First is the section How to Use This Book followed by a short introduction. Next is A Short History of Chemistry, the narrative of which progresses from prehistoric times to the Age of Alchemy and then to the Age of Modern Chemistry. Next is the section titled Atomic Structure, which traces the history of our knowledge of the structure of the atom some theoretical models, including quantum mechanics the discovery of subatomic (nuclear) particles... 

Determine the arrangement and structure of subatomic particles in atoms. Protons, neutrons, and electrons play a central role in everything chemistry, and you find their most basic properties in this part. 

HADRONS. These are subatomic particles, the strong interactions of which are manifested by the forces lhal hold neutrons and protons together in the atomic nucleus. Hadrons include Ihe proton, the neutron, and pion. among others. These particles show signs of an inner structure, i.e.. they are made up of other panicles, which has led over a period of the last several years to consider the hadrons as combinations of constituents known as quarks. See also Quarks and Particles (Subatomic). 

Models of nuclei have grown in sophistication as new discoveries about subatomic particles have been made. One of the simplest was suggested by Niels Bohr, the Danish scientist who contributed a great deal to our understanding of atomic structure. Bohr compared the nucleus to a drop of liquid. His liquid drop model proposes that nucleons are packed together like the molecules in a liquid. Nucleons at the surface of the... 

An understanding of the structure of the smallest particle of matter, the atom, is very important to understanding how chemical bonds form. Remember that inside the nucleus of the atom, there are subatomic particles called protons and neutrons. Orbiting the nucleus is another type of subatomic particle, called electrons. Electrons are the parts of the atom that take part in chemical bonding. Chemical bonds occur when atoms gain, lose, or share electrons. Chemical reactions happen when these chemical bonds are formed or when they are broken. 

The ultimate structures or components of reality (top) are subatomic particles, when I was a high school student, only a few such particles were known and many scientists thought that electrons, protons, and neutrons were the basics whose arrangement in patterns accounted for the way the world was. Now literally hundreds of subatomic particles have been "discovered." The word is enclosed in quotation marks because, of course, no one has actually ever seen a subatomic particle. They are assumed to exist because their presence enables sensible interpretation of various kinds of instrumental readings. Thus modern physicists picture the universe as composed of hundreds of subatomic particles being influenced by three basic types of forces (1) the nuclear binding forces, which operate only at the extremely tiny distances inside atomic nuclei i i - uis pi... 

In the study of chemistry, the atom is the basic structure of matter and protons, electrons, and neutrons are basic subatomic particles. In the study of art, design is the basis of an artistic arrangement, and color is one element of design. The design of a work of art includes not only color but also line, texture, light and dark contrast, and shape. However, color is the element of design that arouses the most appreciation and is the element to which we are most sensitive. Even one who is puzzled by modem art usually finds its color exciting and attractive. One may question the use of distortion of shape but will seldom object to the use of color and may like a work of art solely for its use of color. 

In the 1930 s, the Rutherford proposals of subatomic particles (positive charges) forced to Chadwick to do some experiments. Chadwick thought that if the positive particles (protons) occupy the center of an atom, then since same charged particles would repel each other and the structure of atoms would eventually be destroyed. However, the atom existed and it had a structure. If that was so, Chadwick thought that there must be some other particles holding these protons together in a very small volume . 

It was perhaps Thomson who first suggested a specific structure for the atom in terms of subatomic particles. His plum pudding model (ca. 1900), which placed electrons in a sea of positive charge, like raisins in a pudding., accorded with the then-known facts in evidently permitting electrons to be removed under the influence of an electric potential. The modem picture of the atom as a positive nucleus with extranuclear electrons was proposed by Rutherford13 in 1911. It arose from... 

Elements are defined by the structure of their atoms, determined by the number of each type of subatomic particle present. Each element has been given a name, which is shown in Figure 1.1 as a two-letter abbreviation. These are the abbreviations that are used to write out chemical formulae. 

A better understanding of the structure of the atom came about through additional experiments in the early 1900s. The discovery of the subatomic particles was a major breakthrough in atomic structure. These particles were classified as electrons and nucleons. The nucleons were later found to be neutrons and protons. The properties of these particles can be compared side by side ... 

To use the properties of subatomic particles— protons, electrons, and neutrons—to determine atomic structure... 

In Chapter 3, we learned that atoms owe their characteristics to their subatomic particles— protons, neutrons, and electrons. Electrons occur in regions of space outside the nucleus, and the electronic structure is responsible for all of the atom s chemical properties and many of its physical properties. The number of electrons in a neutral atom is equal to the number of protons in the nucleus. That simple description enables us to deduce much about atoms, especially concerning their interactions with one another (Chapter 5). However, a more detailed model of the atom enables even fuller explanations, including the reason for the differences between main group elements and elements of the ttansition and inner transition series. 

The Nature of Atoms. Ail ordinary matter consists of atoms. The exceptional kinds of matter are. the elementary particles from which atoms are made (electrons, protons, neutrons), and other subatomic particles (positrons, mesons) these elementary particles will be dis cussed later (Chap. 33). But atoms are the units which retain their identity when chemical reactions take place therefore, they are im portant to us now. Atoms are the structural units of all solids, liquids, and gases. They are very small—only about 2 A to 5 A in diameter. 

You will describe the structure of the atom and differentiate among the subatomic particles that comprise it. 

Describe the structure of the nuclear atom, Including the locations of the subatomic particles. 

Subatomic particle research is still a major interest of modern scientists. In fact, the three subatomic particles you have just learned about have since been found to have their own structures. That is, they contain sub-subatomic particles. These particles will not be covered in this textbook because it is not understood if or how they affect chemical behavior. As you will learn in coming chapters, behavior can be explained by considering only an atom s electrons, protons, and neutrons. 

Describe the structure of a typical atom. Be sure to identify where each subatomic particle is located. 

The concept of the elements depended on two different but ultimately complementary ideas about matter. The first idea was ancient that the elements were the fundamental building blocks of nature. Whether there were 1, 2, 3, 4, or 92 elements was in a sense less important than the power of the concept to explain nature and direct research. The second idea came with the discovery of the structure of the atom and the physics that made that discovery possible that an element represented a specific combination of subatomic particles determined by physical laws. The creation of controlled nuclear fission and the invention of accelerators and cyclotrons made a kind of modem alchemy possible, allowing the creation of new elements that were not found in nature but that still met the new conditions to be considered elements. 

The new work led to a physical definition of an element based on atomic structure. According to the physical definition of an element, all the atoms of a particular element have the same number of protons and electrons, although the number of neutrons may vary. The placement of the protons, electrons, and neutrons in the atom follow strict rules of arrangement. The number of subatomic particles and their arrangement then determines the way atoms of elements interact. 

Many other subatomic particles, such as quarks, positrons, neutrinos, pions, and muons, have also been discovered. It is not necessary to study their characteristics to learn the fundamentals of atomic structure that are important in chemical reactions. 

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