Atoms nuclear

The electiomagnetic spectmm is conventionally divided into several energy regions characterized by the different experimental techniques employed and the various nuclear, atomic, and molecular processes that can be studied these are summarized in Table 1. 

Scientists have developed a highly sophisticated view of the structure of the atom. The currently accepted model is called the nuclear atom. We shall present it without trying to show immediately all of the experimental evidence that led to this particular model. Rest assured, though, that every feature of the nuclear atom picture rests upon experimental evidence, as we shall see in Chapter 14. 

Fig. 14-11. The scattering of alpha particles by a foil made of Rutherford nuclear atoms.

The most stable state of the atom would be expected to be the one in which the atom has the lowest energy. Bohr reasoned that since we observe that the nuclear atom does exist then it must be a fundamental fact of nature that an atom can exist in its most stable state indefinitely. Even though this fact could not be rationalized (remember, the earlier laws of physics predicted the atom should collapse) it had to be accepted because it was a result of experiments. 

Rusting, 45, 85, 405 Rutherford, Ernest, 244 Rutherford nuclear atom, 244 scattering experiment, 244 Rutile, 401... 

Read about the gold foil experiment in your textbook. Describe the plum-pudding atomic model. How did the gold foil experiment show the plumpudding model to be in error Describe the nuclear atomic model that replaced the plumpudding model. 

R. S. Freidman and D. G. Truhlar, in Multiparticle Quantum Scattering with Applications to Nuclear, Atomic, and Molecular Physics, eds. D. G. Truhlar and B. Simon (Springer-Verlag, New York, 1997), p. 243. 

Electrical energy Nuclear (atomic) energy Sound... 

It is not obvious how a stable nuclear atom can be rationalized in terms of a static charge distribution in a Coulomb field, where the force between two charges is given by... 

The first application of quantum theory to a problem in chemistry was to account for the emission spectrum of hydrogen and at the same time explain the stability of the nuclear atom, which seemed to require accelerated electrons in orbital motion. This planetary model is rendered unstable by continuous radiation of energy. The Bohr postulate that electronic angular momentum should be quantized in order to stabilize unique orbits solved both problems in principle. The Bohr condition requires that... 

Nuclear/atomic processes, 21 306-309 Nuclear capacities, regional, 17 567t Nuclear chain reaction, modeling, 17 563 Nuclear collisions, energy loss from,... 

V. A. Mandelshtam, in Multiparticle Quantum Scattering with Applications to Nuclear, Atomic... 

Rutherford s attitude toward chemistry was stereotyped by his jokes and barbs occasionally directed at his chemical colleagues. The later Manchester physicist P. M. S. Blackett recounted the famous crack, "All science is either physics or stamp collecting, "63 and it was said that Rutherford chafed at receiving the 1908 Nobel Prize in chemistry, rather than in Physics. In a lecture in which he described his theory of the nuclear atom, he joked that the "nucleus is a round, hard objectjust like Professor Perkins head."64 However, Rutherford expressed great respect for his chemist collaborator Frederick Soddy and for other chemists, as well. 

The concept of the atom as the smallest particle of matter (from the Greek word for indivisible) was promulgated by John Dalton about 1803. Within about a century and a quarter of scientific investigation which will be briefly described in this chapter, this concept yielded the idea of the periodic table and the understanding of the periodic table including the nuclear atom, the concept of isotopes, and the discovery of the majority of the isotopes which are used in the studies of the isotope effects. It is appropriate to point out that this book deals with the study of the effect of isotopic substitution on the physical and chemical properties of molecular (or atomic) systems. The book does not deal with the use of isotopes as tracers, a use which usually depends on the assumption that isotope effects are small and can be ignored in tracer studies. 

Rutherford s atomic model solved problems inherent in Thomson s atomic model, but it also raised others. For example, an atomic nucleus composed entirely of positive charges should fly apart due to electrostatic forces of repulsion. Furthermore, Rutherford s nuclear atom could not adequately explain the total mass of an atom. The discovery of the neutron, in 1932, eventually helped to settle these questions. 

Polonium is found only in trace amounts in the Earths crust. In nature it is found in pitchblende (uranium ore) as a decay product of uranium. Because it is so scarce, it is usually artificially produced by bombarding bismuth-209 with neutrons in a nuclear (atomic) reactor, resulting in bismuth-210, which has a half-hfe of five days. Bi-210 subsequently decays into Po-210 through beta decay The reaction for this process is Bi( ) Bi — °Po + (3-. Only small commercial milligram amounts are produced by this procedure. 

Because the isotope uranium-235 is fissionable, meaning that it produces free neutrons that cause other atoms to split, it generates enough free neutrons to make it unstable. When the unstable U-235 reaches a critical mass of a few pounds, it produces a self-sustaining fission chain reaction that results in a rapid explosion with tremendous energy and becomes a nuclear (atomic) bomb. The first nuclear bombs were made of uranium and plutonium. Today, both of these fuels are used in reactors to produce electrical power. Moderators (control rods) in nuclear power reactors absorb some of the neutrons, which prevents the mass... 

It was quite the most incredible event . Quoted in G. K. T. Conn and H. D. Turner, The Evolution of the Nuclear Atom (London Iliffe Books, 1965), 136. 

A series of episodes in the historical development of our view of chemical atoms are presented. Emphasis is placed on the key observations that drove chemists and physicists to conclude that atoms were real objects and to envision their stracture and properties. The kinetic theory of gases and measmements of gas transport yielded good estimates for atomic size. The discovery of the electrorr, proton and neutron strongly irtfluenced discttssion of the constitution of atoms. The observation of a massive, dertse nucleus by alpha particle scattering and the measrrrement of the nuclear charge resrrlted in an enduring model of the nuclear atom. The role of optical spectroscopy in the development of a theory of electronic stracture is presented. The actors in this story were often well rewarded for their efforts to see the atoms. 

Moreover, because the nuclei are effectively point charges, it should be obvious that their positions correspond to local maxima in tlie election density (and these maxima are also cusps), so the only issue left to completely specify the Hamiltonian is die assignment of nuclear atomic numbers. It can be shown diat diis information too is available from the density, since for each nucleus A located at an electron density maximum Fa... 

Molybdo-vanadoarsenates.—A number of compounds have been described which are analogous to the molybdo-vanadophosphates described above, and which contain arsenic for the nuclear atom of the complex anion. In many cases these compounds approximate to the... 

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