Subatomic

The ability to control the position of a fine tip in order to scan surfaces with subatomic resolution has brought scanning probe microscopies to the forefront in surface imaging techniques. We discuss the two primary techniques, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) the interested reader is referred to comprehensive reviews [9, 17, 18]. 

Besides particles, the forces of nature play also a key role. In the past century four fundamental forces were recognized the gravitational, electromagnetic, weak, and strong forces. Of these the weak and strong forces are less familiar, because they are nuclear forces and their strength rapidly diminishes over all but subatomic scales. 

A positively charged subatomic particle equivalent to a helium nucleus (a). 

A charged subatomic particle produced when a neutron converts to a proton, or a proton converts to a neutron (p). 

Radioactive materials Elements that have unstable nuclei that spontaneously disintegrate, releasing radiation in the form of subatomic particles and energy. 

S.U., abbrev. (siehe unten) see below. SuaJkingtunmi, n. Suakin gum, talha gum. subaerisch, a. subaerial, subatomar, a. subatomic. 

The development of particle accelerators grew out of the discovery of radioactivity in uranium by Henri Becquerel in Paris in 1896. Some years later, due to the work of Ernest Rutherford and others, it was found that the radioactivity discovered by Becquerel was the emission o particles with kinetic energies o several MeV from uranium nuclei. Research using the emitted particles began shortly thereafter. It was soon realized that if scientists were to learn more about the properties of subatomic particles, they had to be accelerated to energies greater than those attained in natural radioactivity. 

If subatomic particles moving at speeds close to the speed of light collide with nuclei and electrons, new phenomena take place that do not occur in collisions of these particles at slow speeds. For example, in a collision some of the kinetic energy of the moving particles can create new particles that are not contained in ordinaiy matter. Some of these created particles, such as antiparticles of the proton and elec-... 

As you probably know, an atom consists of a dense, positively charged nucleus surrounded at a relatively large distance by negatively charged elections (Figure 1.2). The nucleus consists of subatomic particles called neutrons, which are electrically neutral, and protons, which are positively charged. Because an atom is neutral... 

Subatomic particles, such as electrons and nuclei, arc introduced in Section B. 

The observation that atoms of a single element can have different masses helped scientists refine the nuclear model still further. They realized that an atomic nucleus must contain subatomic particles other than protons and proposed that it also contains electrically neutral particles called neutrons (denoted n). Because neutrons have no electric charge, their presence does not affect the nuclear charge or the number of electrons in the atom. However, they do add substantially to the mass of the nucleus, so different numbers of neutrons in a nucleus give rise to atoms of different masses, even though the atoms belong to the same element. As we can see from Table B.l, neutrons and protons are very similar apart from their charge they are jointly known as nucleons. 

B.9 An unstable atomic nucleus gives off nuclear radiation consisting of particles that have a mass of about 1.7 X 10 kg. The particles are attracted to a negatively charged plate. The radiation consists of what type of subatomic particle ... 

B.10 (a) What characteristics do atoms of carbon-12, carbon-13, and carbon-14 have in common (b) In what ways are they different (Consider the numbers and types of subatomic particles.)... 

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... 

The uncertainty principle has negligible practical consequences for macroscopic objects, but it is of profound importance for subatomic particles such as the electrons in atoms and for a scientific understanding of the nature of the world. 

Since Rutherford s work, scientists have identified other types of nuclear radiation. Some consist of rapidly moving particles, such as neutrons or protons. Others consist of rapidly moving antiparticles, particles with a mass equal to that of one of the subatomic particles but with an opposite charge. For example, the positron has the same mass as an electron but a positive charge it is denoted 3 or f e. When an antiparticle encounters its corresponding particle, both particles are annihilated and completely converted into energy. Table 17.1 summarizes the properties of particles commonly found in nuclear radiation. 

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. 

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