Bismuth-209 (Bi) is an

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

bismuth Bismuth is a chemical element; it has symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs nat ...

, with the longest known

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

of any radioisotope that undergoes α-decay (

alpha decay Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an a ...

). It has 83 protons and a magic number of 126 neutrons, and an atomic mass of 208.9803987 amu (atomic mass units). Primordial bismuth consists entirely of this isotope.

Decay properties

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 Bi undergoes

with a half-life of 20.1 exayears (2.01×10, or 20.1 quintillion years), over 10 times longer than the estimated age of the universe. The heaviest nucleus considered to be stable is now

lead-208 Lead (82Pb) has four observationally stable isotopes: 204Pb, 206Pb, 207Pb, 208Pb. Lead-204 is entirely a primordial nuclide and is not a radiogenic nuclide. The three isotopes lead-206, lead-207, and lead-208 represent the ends of three decay ...

and the heaviest stable monoisotopic element is

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

( gold-197). Theory had previously predicted a half-life of 4.6 years. It had been suspected to be radioactive for a long time. The decay produces a 3.14 MeV

alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...

plus thallium-205. Bismuth-209 forms Tl: : → + 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. Due to its extremely long half-life, Bi 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 Bi 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 ( Te) with a half-life estimated at 7.7 × 10 years by double β-decay (

double beta decay In nuclear physics, double beta decay is a type of radioactive decay in which two neutrons are simultaneously transformed into two protons, or vice versa, inside an atomic nucleus. As in single beta decay, this process allows the atom to move cl ...

). The half-life of Bi was confirmed in 2012 by an Italian team in Gran Sasso who reported years. They also reported an even longer half-life for alpha decay of Bi to the first excited state of Tl (at 204 keV), was estimated at 1.66 years. Even though this value is shorter than the half-life of Te, both alpha decays of Bi hold the record of the thinnest natural line widths of any measurable physical excitation, estimated respectively at ΔΕ~5.5×10 eV and ΔΕ~1.3×10 eV in application of the

uncertainty principle The uncertainty principle, also known as Heisenberg's indeterminacy principle, is a fundamental concept in quantum mechanics. It states that there is a limit to the precision with which certain pairs of physical properties, such as position a ...

(double beta decay would produce energy lines only in neutrinoless transitions, which has not been observed yet).

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 Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

, in cosmetics, in paints,B. Gunter "Inorganic Colored Pigments” in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2012. and in several medicines such as Pepto-Bismol. Alloys containing bismuth-209 such as bismuth bronze have been used for thousands of years.

Synthesis of other elements

Po can be manufactured by bombarding Bi with

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

s in a nuclear reactor. Only around 100 grams of Po are produced each year. Po and Po can be made through the proton bombardment of Bi in a

cyclotron A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Januar ...

Astatine Astatine is a chemical element; it has Symbol (chemistry), symbol At and atomic number 85. It is the abundance of elements in Earth's crust, rarest naturally occurring element in the Earth's crust, occurring only as the Decay chain, decay product ...

can also be produced by bombarding Bi with alpha particles. Traces of Bi have also been used to create

in nuclear reactors. Bi has been used as a target for the creation of several isotopes of

superheavy element Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, or superheavies for short, are the chemical elements with atomic number greater than 104. The superheavy elements are those beyond the actinides in ...

s such as dubnium, bohrium, meitnerium, roentgenium, and nihonium.

Formation

Primordial

In the red giant

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

s of the

asymptotic giant branch The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) lat ...

, 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 In nuclear astrophysics, the rapid neutron-capture process, also known as the ''r''-process, is a set of nuclear reactions that is responsible for nucleosynthesis, the creation of approximately half of the Atomic nucleus, atomic nuclei Heavy meta ...

, or rapid process, which occurs during the first fifteen minutes of

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

s. Bismuth-209 is also created during the r-process.

Radiogenic

Some Bi was created radiogenically from the

neptunium Neptunium is a chemical element; it has chemical symbol, symbol Np and atomic number 93. A radioactivity, radioactive actinide metal, neptunium is the first transuranic element. It is named after Neptune, the planet beyond Uranus in the Solar Syste ...

decay chain In nuclear science a decay chain refers to the predictable series of radioactive disintegrations undergone by the nuclei of certain unstable chemical elements. Radioactive isotopes do not usually decay directly to stable isotopes, but rather ...

. Neptunium-237 is an extinct radionuclide, but it can be found in traces in

uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...

ores because of

neutron capture Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus. Since neutrons have no electric charge, they can enter a nucleus more easily than positively charged protons, wh ...

reactions.

Americium-241 Americium-241 (Am, Am-241) is an isotope of americium. Like all isotopes of americium, it is radioactive, with a half-life of . Am is the most common isotope of americium as well as the most prevalent isotope of americium in nuclear waste. It ...

, which is used in smoke detectors, decays to neptunium-237.

Notes

References

{{Authority control Bismuth Isotopes of bismuth