Atomic structure radioactivity

What Do We Need to Know Already Nuclear processes can be understood in terms of atomic structure (Section B and Chapter 1) and energy changes (Chapter 6). The section on rates of radioactive decay builds on chemical kinetics (particularly Sections 13.4 and 13.5). 

The modern theory of the electronic structure of the atom is based on experimental observations of the interaction of electricity with matter, studies of electron beams (cathode rays), studies of radioactivity, studies of the distribution of the energy emitted by hot solids, and studies of the wavelengths of light emitted by incandescent gases. A complete discussion of the experimental evidence for the modern theory of atomic structure is beyond the scope of this book. In this chapter only the results of the theoretical treatment will be described, These results will have to be memorized as rules of the game, but they will be used so extensively throughout the general chemistry course that the notation used will soon become familiar. 

Nuclear dating has been most helpful in establishing the history of the earth and of the moon and of the meteorites. The fact is, there is no other way of measuring their ages. Prior to the discovery of natural radioactivity in the late 19th century, indirect methods were used to estimate the age of the earth, but there were no real answers until the radioactivity of thorium, uranium, and potassium were discovered and we began to understand atomic structure and to realize that nuclear transformation was essentially independent of the chemical form. 

In 1910 Rutherford wrote to a friend, I think I can devise an atom much superior to J.J. s, for the explanation of and stoppage of alpha and beta particles, and at the same time I think it will fit in extraordinary well with the experimental numbers. Rather than devise a model of the atom based on theoretical ideas as Thomson had done, Rutherford intended to probe atomic structure by bombarding atoms with particles ejected from radioactive atoms. Rutherford felt that experimental physics was the only real physics and that by performing experiments he could gain greater insight into atomic structure than Thomson had been able to get using only theory. 

The book is designed to introduce fundamental knowledge in three areas the history of the atom, the periodic table and radioactivity. We will study the historical development of atomic structure theories, the tendencies of elements in periods and groups, and the types of emissions and uses of radioactivity. 

This was initiated by the first description of the atom structure in 1913 by Ernest Rutherford, a British scientist and Niels Bohr, a Danish scientist. Then came the discovery of the neutron in 1932 by James Chadwick (a British student of Rutherford), the discovery of artificial radioactivity by Irene and Frederic Joliot Curie (Nobel Prize in chemistry in 1935) and finally the discovery of fission in 1938 by Lise Meitner, Otto Hahn and Fritz Strassman (German scientists) which brought Hahn the Nobel Prize for physics in 1944. 

This exercise helps familiarise you with aspects of atomic structure and the uses of radioactivity. 

After helium and argon had been discovered the existence of neon, krypton, xenon, and radon was clearly indicated by the periodic law, and the search for these elements in air led to the discovery of the first three of them radon was then discovered during the investigation of the properties of radium and other radioactive substances. While studying the relation between atomic structure and the periodic law Niels Bohr pointed out that element 72 would be expected to be similar in its properties to zirconium. G. von Hevesy and D. Coster were led by this observation to examine ores of zirconium and to discover the missing element which they named hafnium. 

It should be noted that neutron capture and certain nuclear reactions are the only interactions that can make the receiving medium radioactive, a, P, y and X-rays cannot make a medium radioactive. They can ionize a medium, but that does not make the medium radioactive. An ionized stable atom is not radioactive, because ionization alters only the electron structure of an atom, not the nuclear structure, which determines whether an atom is radioactive or stable. 

The interesting is that the stability of an equilibrium state and of an atomic structure are similar. Without the natural radioactivity the end of atoms seems to be in the infinity, too. 

Joliot-Curie, Frederick. (1900-1958). A French physicist who, along with his wife Irene Joliot-Curie, won the Nobel Prize in chemistry in 1935. His important discoveries included artificial radioactivity. He did much work on atom structure, dematerialization of electrons, and inverse transformation. Work on hormone synthesis and thyroid substances containing radioactively labeled elements was significant. ScD from the University of Paris was followed by a distinguished career filled with honors and appointments. 

The second series of inner transition elements, the actinides, have atomic numbers ranging from 90 (thorium, Th) to 103 (lawrencium, Lr). All of the actinides are radioactive, and none beyond uranium (92) occur in nature. Like the transition elements, the chemistry of the lanthanides and actinides is unpredictable because of their complex atomic structures. What could be happening at the subatomic level to explain the properties of the inner transition elements In Chapter 7, you ll study an expanded theory of the atom to answer this question. 

Near the turn of the 20" century, French scientists discovered radioactivity, the emission of particles and/or radiation from atoms of certain elements. Just a few years later, in 1910, the New Zealand-born physicist Ernest Rutherford (1871-1937) used one type of radioactive particle in a series of experiments that solved this dilemma of atomic structure. 

The phenomena of electrolysis first led to the hypothesis of the atomic structure of electricity. Subsequently the carriers of negative electricity were detected in the free state as the cathode rays and the /3-rays of radioactive substances. Prom the deviation of these rays in electromagnetic fields, the ratio ejm, of charge to mass of the particles, could be determined. It was found that... 

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