Bismuth-209
Encyclopedia
Bismuth-209 is the isotope
of bismuth
with the longest half-life
. It has 83 protons and 126 neutrons, and an atomic mass of 208.9803987 u
. All primordial bismuth is of this isotope. It is a decay product from lead-209 decaying by β-
-decay.
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 Bi-209 undergoes alpha decay
with a half-life of approximately 19 exayears (1.9 years), over a billion
times longer than the current estimated age of the universe
. Theory had previously predicted a half-life of 4.6 years. The decay event produces a 3.14 MeV alpha particle
and converts the atom to thallium-205.
Due to its extraordinarily long half-life, for nearly all applications bismuth-209 can still be treated as if it were both stable and non-radioactive. Although bismuth-209 holds the record for alpha decay, bismuth does not have the longest half-life of any element to be found experimentally—this distinction belongs to tellurium-128 with a half-life estimated at 7.7 x 1024 years by double beta decay
.
In the red giant star
s of the asymptotic giant branch
, the s-process
(slow process) is ongoing to produce bismuth-209 by neutron capture as the heaviest element to be formed. All elements heavier than it are formed in the r-process
, or rapid process, which occurs during the first fifteen minutes of supernova
e.
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
of bismuth
Bismuth
Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead...
with the longest half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
. It has 83 protons and 126 neutrons, and an atomic mass of 208.9803987 u
Atomic mass unit
The unified atomic mass unit or dalton is a unit that is used for indicating mass on an atomic or molecular scale. It is defined as one twelfth of the rest mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of...
. All primordial bismuth is of this isotope. It is a decay product from lead-209 decaying by β-
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
-decay.
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 Bi-209 undergoes alpha decay
Alpha decay
Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle and thereby transforms into an atom with a mass number 4 less and atomic number 2 less...
with a half-life of approximately 19 exayears (1.9 years), over a billion
1000000000 (number)
1,000,000,000 is the natural number following 999,999,999 and preceding 1,000,000,001.In scientific notation, it is written as 109....
times longer than the current estimated age of the universe
Age of the universe
The age of the universe is the time elapsed since the Big Bang posited by the most widely accepted scientific model of cosmology. The best current estimate of the age of the universe is 13.75 ± 0.13 billion years within the Lambda-CDM concordance model...
. Theory had previously predicted a half-life of 4.6 years. The decay event produces a 3.14 MeV alpha particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
and converts the atom to thallium-205.
Due to its extraordinarily long half-life, for nearly all applications bismuth-209 can still be treated as if it were both stable and non-radioactive. Although bismuth-209 holds the record for alpha decay, bismuth does not have the longest half-life of any element to be found experimentally—this distinction belongs to tellurium-128 with a half-life estimated at 7.7 x 1024 years by double beta decay
Double beta decay
Double beta decay is a radioactive decay process where a nucleus releases two beta rays as a single process.In double-beta decay, two neutrons in the nucleus are converted to protons, and two electrons and two electron antineutrinos are emitted...
.
In the red giant star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s of the asymptotic giant branch
Asymptotic Giant Branch
The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass stars. This is a period of stellar evolution undertaken by all low to intermediate mass stars late in their lives....
, the s-process
S-process
The S-process or slow-neutron-capture-process is a nucleosynthesis process that occurs at relatively low neutron density and intermediate temperature conditions in stars. Under these conditions the rate of neutron capture by atomic nuclei is slow relative to the rate of radioactive beta-minus decay...
(slow process) is ongoing to produce bismuth-209 by neutron capture as the heaviest element to be formed. All elements heavier than it are formed in the r-process
R-process
The r-process is a nucleosynthesis process, likely occurring in core-collapse supernovae responsible for the creation of approximately half of the neutron-rich atomic nuclei that are heavier than iron. The process entails a succession of rapid neutron captures on seed nuclei, typically Ni-56,...
, or rapid process, which occurs during the first fifteen minutes of supernova
Supernova
A supernova is a stellar explosion that is more energetic than a nova. It is pronounced with the plural supernovae or supernovas. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months...
e.