From Wikipedia, the free encyclopedia
Jump to: navigation, search

Bismuth-209 is the "virtually stable" isotope of bismuth with the longest known half-life of any radioisotope that undergoes α-decay (alpha decay). It has 83 protons and a magic number (physics) of 126 neutrons, and an atomic mass of 208.9803987 amu (atomic mass units). All of the primordial bismuth is of this isotope. It is also the β daughter of lead-209.



Bismuth-209 was long thought to have the heaviest stable nucleus of any element, but in 2003, Noël Coron and his colleagues at the Institut d’Astrophysique Spatiale in Orsay, France, discovered that 209Bi undergoes alpha decay with a half-life of approximately 600 yottaseconds (1.9×1019 years), over a billion times longer than the current estimated age of the universe. Theory had previously predicted a half-life of 4.6×1019 years. The decay event produces a 3.14 MeV alpha particle and converts the atom to thallium-205.[1][2]

Bismuth-209 will eventually form 205Tl:

+ 4

Due to its extraordinarily long half-life, for nearly all applications 209Bi can still be treated as if it were non-radioactive. Although 209Bi holds the half-life record for alpha decay, bismuth does not have the longest half-life of any radionuclide to be found experimentally—this distinction belongs to tellurium-128 (128Te) with a half-life estimated at 7.7 x 1024 years by double β-decay (beta decay).[4]

Hypothetical decay[edit]

According to the United States Geological Survey, the 2010 world mining output of bismuth was 8,900 tonnes[5] (of which virtually 100% is 209Bi).

Hypothetically, if the entire 2010 output were to be stored until the doubling of the current age of the universe (~13.8 billion years from now), less than 4.5 grams would have decayed based upon Coron's half-life data (which is less than the weight of a US quarter dollar).[notes 1]


210Po can be manufactured by bombarding 209Bi with neutrons in a nuclear reactor. Only some 100 grams of 210Po are produced each year.[6]

Bismuth-209 is widely used in digestive medicines such as Pepto-Bismol.


In the red giant stars of the asymptotic giant branch, the s-process (slow process) is ongoing to produce bismuth-209 and polonium-210 by neutron capture as the heaviest elements to be formed, and the latter quickly decays. All elements heavier than it are formed in the r-process, or rapid process, which occurs during the first fifteen minutes of supernovae.[7]

See also[edit]


  1. ^ 4.48 grams = 8900000000 * (1 - 0.5 ^ (13798000000 / (600 * (10 ^ 24) / 31557600)))
    • 8,900 metric tons * 1000000 grams/metric ton = 8900000000 grams mined in the year 2010
    • 13,798,000,000 years since big bang
    • Half-life of 209Bi = 600 yottaseconds = 600*10^24 seconds
    • 31,557,600 seconds/year
    • Amount decayed = Original amount * (1 - 0.5^(Years to decay / half-life in years))


  1. ^ Dumé, Belle (2003-04-23). "Bismuth breaks half-life record for alpha decay". Physicsweb. 
  2. ^ Marcillac, Pierre de; Noël Coron; Gérard Dambier; Jacques Leblanc; Jean-Pierre Moalic (April 2003). "Experimental detection of α-particles from the radioactive decay of natural bismuth". Nature. 422 (6934): 876–878. Bibcode:2003Natur.422..876D. doi:10.1038/nature01541. PMID 12712201. 
  3. ^
  4. ^ "Archived copy". Archived from the original on 2011-09-28. Retrieved 2013-01-10.  Tellurium-128 information and half-life. Accessed July 14, 2009.
  5. ^ Carlin, James F., Jr. "2010 USGS Minerals Yearbook: Bismuth" (PDF). United States Geological Survey. Retrieved 9 September 2010. 
  6. ^ "Swiss study: Polonium found in Arafat's bones". Al Jazeera. Retrieved 2013-11-07. 
  7. ^ Chaisson, Eric, and Steve McMillan. Astronomy Today. 6th ed. San Francisco: Pearson Education, 2008.