Top Qs
Timeline
Chat
Perspective
Bismuth-209
Isotope of bismuth From Wikipedia, the free encyclopedia
Remove ads
Bismuth-209 (209Bi) is an 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[2] of 126 neutrons,[2] and an atomic mass of 208.9803987 Da. Primordial bismuth consists entirely of this isotope.
Remove ads
Decay properties
Summarize
Perspective
Bismuth-209 was long thought to have the heaviest stable nucleus of any element, but in 2003, a research team at the Institut d'Astrophysique Spatiale in Orsay, France, discovered that 209Bi undergoes alpha decay with a half-life of 20.1 exayears (2.01×1019, or 20.1 quintillion years),[3][4] over 109 times longer than the estimated age of the universe.[5] The heaviest nucleus considered to be stable is now lead-208 and the heaviest stable monoisotopic element is gold (gold-197).
Theory had previously predicted a half-life of 4.6×1019 years. It had been suspected to be radioactive for a long time.[6] The decay produces a 3.14 MeV alpha particle plus thallium-205.[3][4]
.svg)
Bismuth-209 forms 205Tl:
- 209
83Bi → 205
81Tl + 4
2He[7]
If perturbed, it would join in lead-bismuth neutron capture cycle from lead-206/207/208 to bismuth-209, despite low capture cross sections. Even thallium-205, the decay product of bismuth-209, reverts to lead when fully ionized.[8]
Due to its extremely long half-life, 209Bi can be treated as non-radioactive for nearly all applications. It is much less radioactive than human flesh, so it poses no real radiation hazard. Though 209Bi holds the half-life record for alpha decay, it does not have the longest known half-life of any nuclide; this distinction belongs to tellurium-128 (128Te) with a half-life estimated at 7.7×1024 years by double β-decay (double beta decay).[9][10][11]
The half-life of 209Bi was confirmed in 2012 by an Italian team in Gran Sasso who reported (2.01±0.08)×1019 years. They also reported an even longer half-life for alpha decay of 209Bi to the first excited state of 205Tl (at 204 keV), was estimated at 1.66×1021 years.[12] Even though this value is shorter than the half-life of 128Te, both alpha decays of 209Bi hold the record of the thinnest natural line widths of any measurable physical excitation, estimated respectively at ΔΕ ≈ 5.5×10−43 eV and ΔΕ ≈ 1.3×10−44 eV in application of the uncertainty principle[13] (double beta decay would produce energy lines only in neutrinoless transitions, which has not been observed yet).
Remove ads
Applications
Because all primordial bismuth is bismuth-209, bismuth-209 is used for all normal applications of bismuth, such as being used as a replacement for lead,[14][15] in cosmetics,[16][17] in paints,[18] and in several medicines such as Pepto-Bismol.[5][19][20] Alloys containing bismuth-209 such as bismuth bronze have been used for thousands of years.[21]
Synthesis of other elements
210Po can be manufactured by bombarding 209Bi with neutrons in a nuclear reactor.[22] Only around 100 grams of 210Po are produced each year.[23][22] 209Po and 208Po can be made through the proton bombardment of 209Bi in a cyclotron.[24] Astatine can also be produced by bombarding 209Bi with alpha particles.[25][26][27] Traces of 209Bi have also been used to create gold in nuclear reactors.[28][29]
209Bi has been used as a target for the creation of several isotopes of superheavy elements such as dubnium,[30][31][32][33] bohrium,[30][34] meitnerium,[35][36][37] roentgenium,[38][39][40] and nihonium.[41][42][43]
Remove ads
Formation
Primordial
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,[44] and the latter quickly decays.[44] All elements heavier than it are formed in the r-process, or rapid process, which occurs during the first fifteen minutes of supernovas.[45][44] Bismuth-209 is also created during the r-process.[44]
Radiogenic
Some 209Bi was created radiogenically from the neptunium decay chain.[46] Neptunium-237 is an extinct radionuclide, but it can be found in traces in uranium ores because of neutron capture reactions.[46][47] Americium-241, which is used in smoke detectors,[48] decays to neptunium-237.
See also
Notes
- Red horizontal lines with a circle in their right ends represent neutron captures; blue arrows pointing up-left represent beta decays; green arrows pointing down-left represent alpha decays; cyan/light-green arrows pointing down-right represent electron captures.
Remove ads
References
Wikiwand - on
Seamless Wikipedia browsing. On steroids.
Remove ads