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Chemistry

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    $\begingroup$ Nuclear properties have absolutely nothing to do with chemistry (f-block and everything). Promethium being radioactive is just bad luck. Technetium is another such case. $\endgroup$
    – Ivan Neretin
    Commented Sep 6, 2016 at 17:13
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    $\begingroup$ Glen Seaborg might disagree a little bit on it being chemistry or not ;), but @IvanNeretin is generally correct. The issue isn't f-electrons so much as nuclear structure, where it turns out that the Samarium nucleus is more tightly bound (see nuclear shell model), so flipping one of Promethium's neutrons to a proton results in a lower-energy nucleus (not that it stops there in general, but...). $\endgroup$
    – Jon Custer
    Commented Sep 6, 2016 at 17:20
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    $\begingroup$ It is not the only radioactive lanthanide. It is the only one with no stable isotopes. Other stable lanthanides also have naturally occurring radioactive isotopes (samarium is a good example). $\endgroup$
    – Gimelist
    Commented Sep 7, 2016 at 5:51
  • $\begingroup$ @IvanNeretin I would advise against making such a sweeping absolutist statement. It is well-established that nuclear properties can affect chemical properties. Granted, it's not typical, but it's nevertheless incorrect to take the hard-line stance that it doesn't happen at all. See, for instance: tandfonline.com/doi/abs/10.1080/00222348808212315?src=recsys $\endgroup$
    – theorist
    Commented Apr 1, 2020 at 5:58
  • $\begingroup$ @theorist See, in natural sciences there is always an exception, or a subtlety, or a tiny deviation in nearly any rule and law. If we start with exceptions, the students never get to know the rules in the first place. Here I stand, and I can do no other. $\endgroup$
    – Ivan Neretin
    Commented Apr 1, 2020 at 6:06