In nuclear physics, there are certain special values for the number of
protons or the number of neutrons that keep popping up. Those are the
values shown by horizontal and diagonal lines in the decay plot figure
magic numbers were historically found to be
associated with unusual stability properties. For example, the magic
number of 82 neutrons occurs in 7 stable nuclei, more stable nuclei
than for any other number of neutrons. The runners-up are 20 and 50
neutrons, also both magic numbers, that each occur in 5 stable nuclei.
Nuclei that have a magic number of protons also tend to have unusual
stability. For example, the element with the most stable isotopes is
tin, with 10 of them. Tin has
The last element to have any stable isotopes at all is lead, and its
number of protons
The doubly magic
Nuclei with magic numbers also have unusually great isotopic presence on earth as well as cosmic abundance. The reason for the magic numbers will eventually be explained through a simple quantum model for nuclei called the “shell model.” Their importance will further be apparent throughout the figures in this chapter.