Radioactivity is the emanation of various atomic particles and rays (energy) from certain elements that have unstable atomic structures (e.g., isotopes). The emanations of radium (chiefly Ra226*), for example, are (1) alpha rays (particles) that are actually helium nuclei (2P++ plus 2N00) traveling at about one fifth the speed of light; (2) beta rays or particles (actually stream of electrons) moving at nearly the speed of light; and (3) gamma rays.
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The last are nonparticulate radiant energy somewhat like hard (i.e., short and penetrating) X-rays. They move at the speed of light (186,000 mi/sec.). Radioactivity is isotopes is derived from instability of their nuclei only, and is fully manifested and detectable with a Geiger counter whether the isotopes are free or combined in compounds.
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Stability of an atomic nucleus is greatest when the numbers of protons and neutrons are equal; a ratio of 1:1. If too great a discrepancy exists in this ratio, in either direction, the nucleus is unstable and tend to adjust the ratio to greater stability by giving off energy in the form of various radioactive emanations.
Adjustments are made toward greater stability by alterations in structure of the nucleus such as transformation of neutrons into protons by splitting off electrons from the neutrons.
For example, the unstable (radioactive) carbon isotope 6C14, with 6 protons and 8 neutrons (a proton: neutron ratio of 3:4), loses an electron from one neutron and thus gains one proton, becoming the stable form of nitrogen (7N14) with 7 each of protons and neutrons. The electron escapes with its energy; a beta particle. Transmutation of one element into another has occurred.
Radioactive isotopes of a number of elements are commonly manufactured by shooting their nuclei with high-velocity atomic particles; neutrons, protons, alpha particles or gamma rays. For example, bombarding normal nitrogen atoms (at. wt. 14) with neutrons made to travel at extremely high speeds by means of an accelerator (icyclotron or synchrotron) splits the nitrogen nucleus, yielding radioactive heavy carbon (C14*).
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C14* is produced in considerable amounts in atomic bomb explosions. Because carbon enters into organic compounds, C14* eventually gains entrance into the cells and tissue of living human beings.
As will be detailed later, radioactivity is an important cause of genetic mutates (altered inherited characteristics) and of cancer, hence isotopes in fallout are of intense interest not only to biologists but to everyone else.
Since the nuclei of radioactive isotopes constantly give off nuclear particles and energy, the nuclei eventually become altered: i.e., they decay. The element finally changes into another element of lower atomic number.
For example, the nucleus of uranium (at. no = 92; or 92U238) becomes a thorium nucleus (at. no = 90; i.e. Th232) by losing an alpha particle; the radium nucleus (at. no. = 88) becomes a radon nucleus (at. no = 86) in the same way.
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When a beta particle is given off in radioactivity, a neutron (an electron combined with a proton) splits, permitting the electron to leave the decomposing nucleus. The neutron residue remains in the nucleus as a proton.
The atomic number (number of orbital electron) is thus increased and the element changes into another; for example, uranium (at. no 92) becomes first neptunium (at. no 93) and then plutonium (at. no. 94).
The emanation of gamma rays involves only loss of energy, which does not cause alteration in either atomic weight or number although it occurs during both alpha and beta radiations.
All of these nuclear modifications result in the transmutation of substances—the mysterious change those medieval alchemists, wholly ignorant of atomic structure or the true nature of matter, tried so long and so hard to achieve with the aid of abracadabra and other incantations in order to make gold from lead! Many an ambitious prince of bygone centuries subsidized at court alchemist who never in his life came nearer to the secrete of “the philosopher’s stone” than the causing of weird light and horrible odors! Often, instead of gaining a fortune, he lost his head.