Bismuth-209
Bismuth-209 is the "virtually stable" isotope of bismuth with the longest half-life of any radioisotope that undergoes α-decay (alpha decay). It has 83 protons and 126 neutrons, and an atomic mass of 208.9803987 amu (atomic mass units). All primordial bismuth is of this isotope. It is a β−product of lead-209.
Stability
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 can undergo alpha decay and is produced as part of the decay of Americium-241 (241Am):
- 209
82Pb → 209
83Bi + e−
Bismuth-209 will eventually form 205Tl:
- 209
83Bi → 205
81Tl + 4
2He[3]
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
According to the United States Geological Survey, the 2010 world mining output of Bismuth was 8,900 metric 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]
Uses
210Po can be manufactured by bombarding 209Bi with neutrons in a nuclear reactor. Only some 100 grams of 210Po are produced each year.[6]
Formation
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
Notes
- ↑ 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))
References
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ http://periodictable.com/Isotopes/095.241/index.full.html
- ↑ http://presolar.wustl.edu/work/noblegas.html Tellurium-128 information and half-life. Accessed July 14, 2009.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Chaisson, Eric, and Steve McMillan. Astronomy Today. 6th ed. San Francisco: Pearson Education, 2008.
