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The half lives of many radioactive isotopes have been measured directly. But are their half-lives known to be a function of their composition?

In other words, can someone say "given an atom with this many protons, neutrons and electrons, and given the known strengths and ranges of the various forces at play inside an atom, we can quantify how unstable such an atom would be by saying that a collection of them would have a half-life of X"?

Has such a prediction ever been made about an isotope before people had encountered it, then later borne out by experiment?

Nathan Long
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    I think the answer is probably technically no: it was not until fairly recently that we knew bismuth is actually radioactive, albeit with a ludicrously long lifetime. But this is an excellent question, particularly if lifetimes are restricted to a billion years or so. – Ed V May 26 '20 at 02:49
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    Actaully $^{209}\ce{Bi}$ would seem to be an example. Theorists had evidently long suspect that the isotope was radioactive. See for example: "A SEARCH FOR α-PARTICLES FROM THE DECAY OF Bi209" E. P. Hincks and , C. H. Millar, Canadian Journal of Physics, 1958, 36(2): 231-251, https://doi.org/10.1139/p58-027 – MaxW May 26 '20 at 05:17
  • @EdV What is supposed to be excellent about it? Unless clarified, I don't think this question is OK, at all. There are theories of nuclear structure and all kinds of predictions. Maybe about only thing that would make this viable is the notion of accuracy. If clarified - how accurate is accurate enough. – Mithoron May 26 '20 at 13:15
  • @Mithoron My thought was that making an accurate prediction, and then finding experimental verification, is what science is about. I agree completely about the accuracy aspect. The bismuth example had a predicted range that was way too large and the experimental half-life was near the lower end. I am not impressed with that. If a new isotope were to be created and had an experimental half-life within 10 or 20% of an a priori prediction of the half-life, I would be impressed and say it was a significant achievement. But YMMV. – Ed V May 26 '20 at 13:33
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    @Mithoron My apologies if my question doesn't meet your standards. I'm very much a beginner. My motivation: decay rates are used in radiometric dating, and young earth creationists sometimes allege that decay rates may have changed. I'd like to know if there exists a function that can accurately tell us the half life of any isotope based on its structure and the basic nuclear forces, such that half lives can't have changed unless nuclear forces have. An accurate prediction would be strong validation for such a function. I would leave quantifying the accuracy to the judgment of respondents. – Nathan Long May 26 '20 at 13:52
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    Other options would be the relatively recently created elements, but there good accuracy of the predicted lifetimes is getting within an order of magnitude. – Jon Custer May 26 '20 at 14:10
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    @NathanLong - Don't waste any effort trying to convince young earth creationists that their belief is wrong. They have seen "The Flintstones" on TV and know that people and dinosaurs roamed the earth together. Corollary:"Never try to teach a pig to sing. It frustrates you and annoys the pig." – MaxW May 26 '20 at 20:03
  • @MaxW There are definitely those who can't be persuaded, but don't write people off categorically. Good arguments persuaded me away from YEC, and there are many personal stories on the BioLogos website of a similar nature. I continue to try to improve my understanding of how all the pieces of evidence fit together. The most helpful explanations to me are those that tell not only what is known, but how we know it. Those are the kinds I want to offer in my own conversations. – Nathan Long May 27 '20 at 01:59

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A quick perusal of the post-WWII literature (particularly Glenn Seaborg) pulls up papers like The New Element Californium (Atomic Number 98) where comparisons of the observed alpha decay half life are said to be in line with predictions. Such predictions follow along from papers such as Systematics of Alpha-Radioactivity.

So, yes, it would seem that predictions of radioactive half lives were part and parcel of the creation of new elements in the laboratory.

Jon Custer
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