Radioactive series nuclear

The part of the radioactive series b ioning at radium is own bdow with the nature of the particles emitted and the half-value periods (Mattauch, Nuclear physical tables", Intersdence, 1946). 

Some nuclei cannot gain stability by a single emission. Consequently, a series of successive emissions occurs as shown for uranium-238 in A FIGURE 21.3. Decay continues until a stable nucleus—lead-206 in this case—is formed. A series of nuclear reactions that begins with an unstable nucleus and terminates with a stable one is known as a radioactive series or a nuclear disintegration series. Three such series occur in nature uranium-238 to lead-206, uranium-235 to lead-207, and thorium-232 to lead-208. 

SECTION 21.2 The neutron-to-proton ratio is an important factor determining nuclear stability. By comparing a nuclide s neutron-to-proton ratio with those in the band of stability, we can predict the mode of radioactive decay. In general, neutron-rich nuclei tend to emit beta particles proton-rich nuclei tend to either emit positrons or im-dergo electron capture and heavy nuclei tend to emit alpha particles. The presence of magic numbers of nucleons and an even number of protons and neutrons also help determine the stability of a nucleus. A nuclide may undergo a series of decay steps before a stable nuclide forms. This series of steps is called a radioactive series or a nuciear disintegration series. 

The exponential laws of radioactive-series decay and growth of radionuclides were first formulated by Rutherford and Soddy in 1902, to explain their results (Rutherford and Soddy 1902,1903) on the thorium series of radionuclides. In 1910, Bateman (Bateman 1910) derived generalized mathematical expressions that were used to describe the decay and growth of the naturally occurring actinium, uranium, and thorium series until the discovery of nuclear fission and other new radioactive decay series were found in the 1940s. For the description of half-lives and decay constants, activities and number of radionuclides involved in the decay of two radionuclides, Friedlander et al. (1981) have given a representative overview (see also O Chap. 5 in Vol. 1). 

Natural Radioactive Decay Series—Nuclear Equations... 

As chemists write chemical equations to describe chemical changes, they write nuclear equations to describe nuclear changes. A nuclear equation shows the reactant nuclides or particles on the left and the product nuclides or particles on the right. The first step in the natural radioactive series observed by Becquerel is an alpha decay reaction. In it, a nucleus disintegrates, or decays, into a He nucleus (alpha particle) and a nucleus. The nuclear equation is... 

Cerium, an element in the lanthanide series, has a number of radioactive isotopes. Several of these are produced in abundance in nuclear fission reactions associated with nuclear industry operations or detonation of nuclear devices. This report summarizes our present knowledge of the relevant physical, chemical, and biological properties of radiocerium as a basis for establishing radiation protection guidelines. 

Because radioactive decay is a nuclear process, the rate of radioactive decay is totally unaffected by any external factors. Unlike chemical reactions, therefore, there is no dependency on temperature, or pressure, or any of the other environmental factors which affect the rate at which normal chemical reactions occur. This is the reason why radioactive decay chronometers, such as 14C, Ar-Ar, and U-series methods, are so important in geology and archaeology - they provide an absolute clock . 

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