The binding energy per nucleon in MeV ( highest numbers in dark red, in excess of 8.5 MeV per nucleon ) is plotted for various nuclides as a function of " Z ", the atomic number ( on the y-axis ), vs . " N ", the neutron number ( on the x-axis ).
32.
Because, for even " Z " ( proton number ) and even " N " ( neutron number ) nuclei, there is a gap from ground state to first excited particle state which is reached by nucleon pair breaking fragments with even " Z " is expected to have a higher probability to be produced than those with odd " Z ".
33.
Of particular note is Ubh-310, which would be " doubly magic " ( both its proton number of 126 and neutron number of 184 are thought to be magic ) and thus the most likely to have a very long half-life . ( The next lighter doubly magic spherical nucleus is lead-208, the heaviest known stable nucleus and most stable heavy metal . )"
34.
Because of the energy gain from nuclear pairing effects, the odd number of protons imparts instability to isotopes of an odd "'Z "', which in heavier elements requires a completely paired set of neutrons to offset this tendency into stability . ( The four stable nuclides with odd "'Z "'and odd neutron numbers are hydrogen-2, lithium-6, boron-10, and nitrogen-14 ).
