1355 Chapter 40 Nuclear Physics Conceptual Problems 1•Determine the ConceptTwo or more nuclides with the same atomic number Z but different Nand Anumbers are called isotopes. (a) Two other isotopes of 14N are: 15N, 16N (b) Two other isotopes of 56Fe are: 54Fe, 55Fe (c) Two other isotopes of 118Sn are: 54Fe, 55Fe 2•Determine the ConceptThe parent of that series, 237Np, has a half-life of 2×106y that is much shorter than the age of the earth. There is no naturally occurring Np remaining on earth.3•Determine the ConceptGenerally, β-decay leaves the daughter nucleus neutron rich, i.e., above the line of stability. The daughter nucleus therefore tends to decay via β– emission which converts a nuclear neutron to a proton.*4•Determine the Concept 14C is found on earth because it is constantly being formed by cosmic rays in the upper atmosphere in the reaction 14N + n →14C + 1H.5 •Determine the ConceptIt would make the dating unreliable because the current concentration of 14C is not equal to that at some earlier time.6 •Determine the ConceptAn element with such a high Zvalue would either fission spontaneously or decay almost immediately by αemission (see Figure 40-3).7• Determine the ConceptThe probability for neutron capture by the fissionable nucleus is large only for slow (thermal) neutrons. The neutrons emitted in the fission process are fast (high energy) neutrons and must be slowed to thermal neutrons before they are likely to be captured by another fissionable nucleus.
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