| In nuclear physics, a magic number is a number of nucleons (either protons or neutrons) such that they are arranged into complete shells within the atomic nucleus. The seven known magic numbers as of 2007 are;
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| 2, 8, 20, 28, 50, 82, 126 |
| Atomic nuclei consisting of such a magic number of nucleons have a higher average binding energy per nucleon than one would expect based
upon predictions such as the semi-empirical mass formula and are hence more stable against nuclear decay.
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| The unusual stability of isotopes having magic numbers means that transuranium elements can be created with extremely large nuclei and yet not be subject to
the extremely rapid radioactive decay normally associated with high atomic numbers (as of 2007, the longest-lived, known isotope
among all of the elements between 110 and 120 lasts only 3.6 seconds). Large isotopes with magic numbers of nucleons are said
to exist in an island of stability. Unlike the magic numbers 2-126, which are realized in spherical nuclei, theoretical calculations predict that nuclei in
the island of stability are deformed. Before this was realized, higher magic numbers, such as 184, were predicted based on
simple calculations that assumed spherical shapes. It is now believed that the sequence of spherical magic numbers cannot
be extended in this way.
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See Also