Artificial Transmutations of Elements

Moderate irradiation with gamma-rays from radioactive isotopes has kept the strawberries at the right fresh for 15 days, whiie those at the ieft are moldy. Such irradiation kills mold spores but does no damage to the food. The food does not become radioactive. 

In addition to the Pu-based heart pacemaker already mentioned, lightweight, portable power packs that use radioactive isotopes as fuel have been developed for other uses. Polonium-210, californium-242, and cahfomium-244 have been used in such generators to power instruments for space vehicles and in polar regions. These generators can operate for years with only a small loss of power. 

The pathways of chemical reactions can be investigated using radioactive tracers. When radioactive ions are added to a saturated solution of cobalt sulfide in equilibrium with solid cobalt sulfide, the solid CoS becomes radioactive. This shows that sulfide ion exchange occurs between solid and solution in the solubility equilibrium. 

Photosynthesis is the process by which the carbon atoms in CO2 are incorporated into glucose, C6H12O6, in green plants. 

A weakly radioactive source such as americium is used iu some smoke detectors. Radiatiou from the source iouizes the air to produce a weak curreut. Smoke particles iuterrupt the current flow by attracting the ions. This decrease in current triers the alarm. 

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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. 

Nuclei with Atomic Number Greater Than 83 Detection of Radiation Rates of Decay and Half-Life Disintegration Series Uses of Radionuclides Artificial Transmutations of Elements Nuclear Fission Nuclear Fission Reactors Nuclear Fusion... 

Equations for Nuclear Reactions 26-13 Artificial Transmutations of Elements... 

Rutherford was the first to carry out artificial transmutation of elements. In 1919 he bombarded nitrogen with alpha particles and obtained oxygen atoms. This first in history... 

Detection of Rad iation 22-10 Rates of Decay and Half-Life 22-11 Decay Series 22-12 Uses of Radionuclides 22-13 Artificial Transmutations of Elements 22-14 Nuclear Fission 22-15 Nuclear Fission Reactors 22-16 Nuclear Fusion... 

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

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... 

Geiger and Marsden continued to study the deflection of a-particles, and in 1913 (after observing over 100,000 scintillations at a rate of 5 to 90 per minute) correlated nuclear charge with atomic number. In 1914 and 1915 Marsden continued to study the impact of a-particles on matter these experiments led to Rutherford s 1919 fortuitous attainment of the alchemist s dream the artificial transmutation of the elements. 

As discussed in Chapter 12, in 1919 Rutherford caused artificial transmutation of one element into another by using as projectiles the a-particles emitted in the radioactive decay... 

They could not chemically trace the infinitesimal accumulation of silicon. Joliot explained why in 1935, when he and his wife accepted the Nobel Prize in Chemistry for their discovery The yield of these transmutations is very small, and the weights of elements formed. .. are less than 10 [grams], representing at most a few million atoms —too few to find by chemical reaction alone. But they could trace the radioactivity of the phosphorus with a Geiger counter. If it did indeed signal the artificial transmutation of some of the aluminum to phosphorus, they should be able to separate the two different elements chemically. The radioactivity would go with the new phosphorus and leave the untransmuted aluminum behind. But they needed a definitive separation that could be carried out within three minutes, before the faint induced radioactivity faded below their Geiger counter s threshold. 

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. 

It is now accepted as a proved fact that the element radium decomposes with the formation of other elements, the simplest of which is apparently helium, and the experiments of Sir William Ramsay have indicated that the energy liberated by radium can effect the transmutation of other elements into one another but in such cases man can only watch the changes that go on, and cannot control or vary them. But in the building-up process that has apparently now been discovered, the energy for the change is artificially supplied and controlled, and the changes are thus of a different order from the radioactive decompositions of a decaying element. 

Einsteinium does not exist in nature and is not found in the Earth s crust. It is produced in small amounts by artificial nuclear transmutations of other radioactive elements rather than by additional explosions of thermonuclear weapons. The formation of einsteinium from decay processes of other radioactive elements starts with plutonium and proceeds in five steps as follows ... 

TRANSMUTATION. The natural or artificial transformation of atoms of one element into atoms of a different element as the result of a nuclear reaction. The reaction may be one in which two nuclei interact, as in the formation of oxygen from nitrogen and helium nuclei (/3-particles), or one in which a nucleus reacts widi an elementary particle such as a neutron or proton. Thus, a sodium atom and a proton form a magnesium atom. Radioactive decay, e.g., of uranium, can be regarded as a type of transmutation. The first transmutation was performed bv the English physicist Rutherford in 1919. 

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 ... 

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