Worksheet: The Graph of Nuclear Stability

In this worksheet, we will practice using a plot of proton and neutron numbers for stable nuclei to predict the decay patterns of radioisotopes.


The figure below illustrates the numbers of neutrons, 𝑛 , in known isotopes as a function of their atomic numbers, 𝑍 . Stable (nonradioactive) isotopes lie on a narrow band of stability, indicated in blue.

Which of the following isotopes does not lie within the band of stability?

  • ALead-206
  • BCalcium-40
  • CIron-56
  • DChlorine-37
  • ECarbon-14

Which of the following isotopes is likely to decay by electron capture?

  • AMolybdenum-101
  • BTin-124
  • CSelenium-84
  • DRhodium-97
  • EStrontium-92

Which of the following isotopes is likely to undergo 𝛽 decay?

  • ABismuth-207
  • BGold-197
  • CThallium-209
  • DLead-204
  • EMercury-195

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