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?

  • AChlorine-37
  • BCarbon-14
  • CCalcium-40
  • DIron-56
  • ELead-206

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

  • AMolybdenum-101
  • BStrontium-92
  • CTin-124
  • DRhodium-97
  • ESelenium-84

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

  • AMercury-195
  • BBismuth-207
  • CLead-204
  • DThallium-209
  • EGold-197

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