Stability radioactive series nuclear

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. 

Radioactive decay occurs because of nuclear instability, with the end result of decay being stability. If this stability is not achieved by the first nuclear transformation, then more transformations occur. This set of transformations is called a decay series, as shown in Figure 14.4. 

Because the range of nuclidic stability is bounded by fractions that derive from Fibonacci numbers, it probably means that nuclear stability relates directly to the golden mean. To demonstrate this relationship it is noted that the plot of A vs Z, shown in figure 13 for the A(mod4) = 0 series of nuclides, separates into linear sections of constant neutron excess (A — 2Z) and slope 2. Each section terminates at both ends in a radioactive nuclide. The range of stability for each section follows directly from... 

Nuclei differ in their stability, and some are so unstable that they undergo radioactive decay. The ratio of the number of neutrons to number of protons (N/Z) in a nucleus correlates with its stability. Calculate the N/Z ratio for (a) Sm (b) Fe (c) °Ne (d) ° Ag. (e) The radioactive isotope decays in a series of nuclear reactions that includes another uranium isotope, and three lead isotopes, Pb, °Pb, and ° Pb. How many neutrons, protons, and electrons are in each of these fi ve isotopes ... 

Describe the differences between nuclear and chemical changes identify the three types of radioactive emissions and the types of radioactive decay, and know how each changes A and Z explain how a decay series leads to a stable nuclide write and balance nuclear equations use the N/Zratio to predict nuclear stability and the type of decay a nuclide undergoes ( 23.1) (SPs 23.1-23.3) (EPs 23.1-23.16)... 

We recognize that nuclear stability is determined largely by the neutron-to-proton raSo. For stable nuclei, this ratio increases with increasing atomic number. All nuclei with 84 or more protons are radioactive. Heavy nuclei gain stability by a series of nuclear disintegrations leading to stable nuclei. 

Nuclei outside the belt of stability, as well as all nuclei with Z > 83, tend to be unstable and will undergo radioactive decay through the emission of particles or radiation. The disintegration of a radioactive nucleus is often the beginning of a radioactive decay series, which is a sequence of nuclear reactions that ultimately form a stable isotope. Table 17.3 shows the 14-step decay series of naturally occurring uranium-238. This decay scheme is known as the uranium decay series. Table 17.3 also shows the half-lives (see Chapte U e... 

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