Bismuth: the s-l-o-w-l-y disappearing element.

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Watch bismuth as it disappears before your very eyes! (If you have the patience.) Common bismuth (209Bi) is unstable, having a half life of 1.9 x 1019 years. It is slowly transforming itself into thallium and helium. How slowly? A 50 gram specimen of 209bismuth loses one atom every 1 hour and 40 minutes on the average. At that rate, if Caesar Augustus had collected a newly refined 50 gram specimen in the year A.D. 1, by now it would have shrunk to 49.99999999999999632 grams. Does this process generate radioactivity? Yes, but no need to worry; the general environment is vastly more radioactive. (Certain “hotter” isotopes of bismuth either do not occur in nature or disintegrate so quickly that they do not remain for a significant time in refined samples if they had even been present, which is unlikely.)
[(c) Allen's Treasure House 2017]