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Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, resembles arsenic and antimony. Bismuth is the most naturally diamagnetic of all metals, and only mercury has a lower thermal conductivity. Bismuth has classically been considered to be the heaviest naturally-occurring stable element. Recently, however, it has been found to be very slightly radioactive: its only naturally occurring isotope bismuth-209 decays via alpha decay into thallium-205 with a half-life of more than a billion times the estimated age of the universe. |