Artificial transmutations

First artificial transmutation of an element Nfa.pl gO 192S-8 First abundance data on stars (spectroscopy)... 

Nuclear fission refers to splitting a (large) nucleus into two smaller ones, not including the tiny particles listed in Table 22-3. Nuclear fusion refers to the combination of small nuclei to make a larger one. Both of these types of processes are included in the term artificial transmutation. 

Transmutation means converting one element to another (by changing the nucleus). The first artificial transmutation was the bombardment of N by alpha particles in 1919 by Lord Rutherford. 

Using the elements mentioned in Section 22-13, induced radiation and the artificial transmutation of elements occur with both light elements, like the nonmetals 3H, 12C and 170 as well has heavier elements, like 97Tc, mFr, 210At and 239U, which can be metals, metalloids or nonmetals. Transuranium elements, i.e. the elements with atomic numbers greater than 92 (uranium), must be prepared by nuclear bombardment of other elements. 

Ernest Rutherford, Frederick Soddy, and then Sir William Ramsay documented natural transformations of one element into another in 1902 and 1903. The artificial transmutation of one element into another, however, was first accomplished in 1919 by Rutherford, a physicist. Indeed, the field of nuclear physics has contributed the most to our understanding of the subatomic world since the 1920s. But the scientists who most advocated transmutation as a goal of research and a heuristic principle for understanding the nature of matter—the Nobel Prize winners Ramsay and Soddy, and, in a less prominent way, Sir William Crookes—were chemists, not physicists.1... 

While some contemporary alchemists such as Hunter, Emmens, Jollivet-Castelot, and Ayton had indeed tried to make gold, Ramsay s attempted transmutations led to a rush toward a different kind of treasure scientific immortality. Multiple chemists pursued the same kinds of experiments that Ramsay had, believing that they too had found positive results. They attempted to position themselves within the scientific world as the first to have proven artificial transmutation. Between 1907, when Ramsay announced his supposed copper transmutations in Nature, and 1914, when he abandoned his efforts, several significant chemists (including J. N. Collie, Hubert Patterson, E. C. C. Baly, Thomas Merton, Irvine Masson, and A. C. G. Egerton) all participated in experiments to use either radium emanation or cathode rays and X-rays to cause chemical transmutation. 

Artificial transmutations into other stable elements had also been accomplished. 

ATOMIC SPECIES. A distinctive type of atom. The basis of differentiation between atoms is (1) mass, (2) atomic number, or number of positive nuclear charges, (3) nuclear excitation energy. The reason for recognizing this third class is because certain atoms are known, chiefly among those obtained by artificial transmutation, which have the same atomic (isotopic) mass and atomic number, but differ in energetics. 

Morgan TH (1926) Genetics and the physiology of development Am Nat 60 489-515 Muller HJ (1927) Artificial transmutation of the gene. Science 46 84-87 Muller HJ (1951) The development of the gene theory. In Dunn LC (ed) Genetics in the twentieth century. Macmillan, New York, pp 77-100... 

Note that in equation (10), as in the other nuclear equations listed, atomic numbers and mass numbers are both conserved. This reaction was the first artificial transmutation, carried out (as contrasted to spontaneous transmutations or natural radioactivity in which one nucleus is transformed to another, irrespective of the influence of man). The a particle in equation (10) is the projectile and the nitrogen nucleus the target. 

The most important transmutations by a particles are of the (a,p) and (a,n) types. The (a,p) processes (for example, Na23(a,p)Mg26) are common with targets of low atomic weights (Z > 25) as has been seen, these were the first artificial transmutations to be studied. The (a,n) reactions (and the closely related reactions in which two, three, or more neutrons are ejected by a particles of high energy) are of considerable interest in connection with the synthesis of the transuranium elements and of astatine (element 85). The following are typical and important examples ... 

The two problems presented above show a type of transmutation not yet encountered in this book. In these problems an isotope is being bombarded with a particle to trigger the transmutation. This is called an artificial transmutation. This is different from the first four reactions examined, in which the isotopes underwent a natural transmutation and did not need to be bombarded with other particles to undergo a transmutation. The natural transmutations that Th-232 undergoes can be seen in the decay series shown in Figure 12.1. 

The concept of artificial transmutation can be applied to reactions that involve nuclear fission or the splitting of nuclei. An example of this is the fission reaction that occurs in an atomic bomb. When U-235 is bombarded with a neutron, the uranium is split according to the reaction ... 

In the artificial transmutation 94Be + X — 63Li + 42He, the particle represented by the letter X is a(n)... 

These reactions are examples of artificial transmutation—the change of one element into another. Several small particles, in addition to those involved in natural radioactivity, are involved in artificial nuclear reactions. Some of these additional particles are listed in Table 21.4. They are used as projectiles to bombard nuclei or are produced along with other products of such reactions, or both. 

Nuclear chemistry (radiochemistry) has now become a large and very important branch of science. Over four hundred radioactive isotopes have been made in the laboratory, whereas only about three hundred stable isotopes have been detected in nature. Three elements —technetium (43), astatine (85), and promethium (61), as well as some trans-uranium elements, seem not to occur in nature, and are available only as products of artificial transmutation. The use of radioactive isotopes as tracers has become a valuable technique in scientific and medical research. The controlled release of nuclear energy promises to lead us into a new world, in which the achievement of man is no longer limited by the supply of energy available to him. 

The following equation shows an example of an artificial transmutation, as curium-244 is bombarded with carbon-12 to form nobelium-254 ... 

The first artificial transmutation was observed in 1919 by Rutherford, who converted 7N... 

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