This may be nuclear physics more than chemistry, but: To an Ordinary Civilian it looks almost numerological that Technetium and Promethium have no stable isotopes. Do you as a chemist have any insights or casual musings about this peculiarity of the periodic table? Does nature just abhor collections of 43 or 61 protons?
I don't off the top of my head, but it seems to suggest some weird tension between the various forces that hold atomic nuclei together, which are still not nearly as well understood as people might think. it's such a bizarre business: why do neighboring nuclei have lots of stable isotopes while technetium and promethium have none? I did find this, but I confess that I don't fully understand the explanation: this "rule" seems to be one of those semi-empirical things. https://en.m.wikipedia.org/wiki/Mattauch_isobar_rule
~Chara