Chart of the Nuclides

[Robert Monsalve-Jones (Robert Monsalve-Jones) <RMonsalveJones@ITCRP.COM>]

OK group, put on your thinking caps.
a colleague in my office asked why there is more Cs-137 then Cs-135
produced as a result of fission of U-235 (U-236). Referring to the Chart of
the Nuclides (Chart) the fission yields indicate that the Cs-135 should be
slightly more then Cs-137. Now, a reason given by a classmate was that
Cs-137 falls in the "magic number" column as indicated on the Chart. 
On the Chart around certain "N" number columns and "Z" number rows
the lines are bolded. There is no explanation, that I can find, of the bolded
columns and rows given in the manual that came with the Chart.
Does someone out there have the explanation.
Reply in private or to the group as a whole.
Standard disclaimers, these are my own thoughts and questions.

Thanks in advance
Robert Monsalve-Jones
(505) 662-1200
rmjones@itcrp.com