![Table isotopes en](https://upload.wikimedia.org/wikipedia/commons/c/c4/Table_isotopes_en.svg)
Beta-decay stable
isobars are the set of
nuclides
A nuclide (or nucleide, from nucleus, also known as nuclear species) is a class of atoms characterized by their number of protons, ''Z'', their number of neutrons, ''N'', and their nuclear energy state.
The word ''nuclide'' was coined by Truman ...
which cannot undergo
beta decay
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta particle (fast energetic electron or positron) is emitted from an atomic nucleus, transforming the original nuclide to an isobar of that nuclide. For ...
, that is, the transformation of a
neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons beh ...
to a
proton or a proton to a neutron within the
nucleus
Nucleus ( : nuclei) is a Latin word for the seed inside a fruit. It most often refers to:
*Atomic nucleus, the very dense central region of an atom
* Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA
Nucl ...
. A subset of these nuclides are also stable with regards to
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 clos ...
or theoretically higher simultaneous beta decay, as they have the lowest energy of all nuclides with the same
mass number
The mass number (symbol ''A'', from the German word ''Atomgewicht'' tomic weight, also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approxima ...
.
This set of nuclides is also known as the line of beta stability, a term already in common use in 1965. This line lies along the bottom of the nuclear
valley of stability
In nuclear physics, the valley of stability (also called the belt of stability, nuclear valley, energy valley, or beta stability valley) is a characterization of the stability of nuclides to radioactivity based on their binding energy. Nuclide ...
.
Introduction
The line of beta stability can be defined mathematically by finding the nuclide with the greatest
binding energy
In physics and chemistry, binding energy is the smallest amount of energy required to remove a particle from a system of particles or to disassemble a system of particles into individual parts. In the former meaning the term is predominantly use ...
for a given mass number, by a model such as the classical
semi-empirical mass formula
In nuclear physics, the semi-empirical mass formula (SEMF) (sometimes also called the Weizsäcker formula, Bethe–Weizsäcker formula, or Bethe–Weizsäcker mass formula to distinguish it from the Bethe–Weizsäcker process) is used to approx ...
developed by
C. F. Weizsäcker. These nuclides are local maxima in terms of binding energy for a given mass number.
All odd mass numbers have only one beta decay stable nuclide.
Among even mass number, six (124, 130, 136, 148, 150, 154) have three beta-stable nuclides. None have more than three; all others have either one or two.
*From
2 to 34, all have only one.
*From 36 to 72, only eight (36, 40, 46, 50, 54, 58, 64, 70) have two, and the remaining 12 have one.
*From 74 to 122, three (88, 90, 118) have one, and the remaining 23 have two.
*From 124 to 154, only one (140) has one, six have three, and the remaining 9 have two.
*From 156 to 262, only eighteen have one, and the remaining 36 have two, though there may also exist some undiscovered ones.
All
primordial nuclides are beta decay stable, with the exception of
40K,
50V,
87Rb,
113Cd,
115In,
138La,
176Lu, and
187Re. In addition,
123Te and
180mTa have not been observed to decay, but are believed to undergo beta decay with an extremely long half-life (over 10
15 years). Non-primordial
247Cm should undergo beta decay to
247Bk, but has also never been observed to do so. Finally,
48Ca and
96Zr have not been observed to undergo beta decay (which is theoretically possible for both), but double beta decay is known for both. All elements up to and including
nobelium
Nobelium is a synthetic chemical element with the symbol No and atomic number 102. It is named in honor of Alfred Nobel, the inventor of dynamite and benefactor of science. A radioactive metal, it is the tenth transuranic element and is the penul ...
, except
technetium
Technetium is a chemical element with the symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. All available technetium is produced as a synthetic element. Naturally occurring technetium is a spontaneous ...
and
promethium, are known to have at least one beta-stable isotope.
List of known beta-decay stable isobars
350 beta-decay stable nuclides are currently known.
Theoretically predicted or experimentally observed
double beta-decay is shown by arrows, i.e. arrows point towards the lightest-mass isobar. (This is sometimes dominated by
alpha decay
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an at ...
or
spontaneous fission, especially for the heavy elements.)
No beta-decay stable nuclide has
proton number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
43 or 61 and no beta-decay stable nuclide has
neutron number
The neutron number, symbol ''N'', is the number of neutrons in a nuclide.
Atomic number (proton number) plus neutron number equals mass number: . The difference between the neutron number and the atomic number is known as the neutron excess: . ...
19, 21, 35, 39, 45, 61, 71, 89, 115, 123, or 147.
![Nuclear chart from KTUY model](https://upload.wikimedia.org/wikipedia/commons/9/9e/Nuclear_chart_from_KTUY_model.svg)
All beta-decay stable nuclides with A ≥ 209 were observed to decay by alpha decay except some where spontaneous fission dominates. With the exception of
262No, no nuclides with A > 260 have been definitively identified as beta-stable.
260Fm and
262No are unconfirmed.
The general patterns of beta-stability are expected to continue into the region of
superheavy element
Superheavy elements, also known as transactinide elements, transactinides, or super-heavy elements, are the chemical elements with atomic number greater than 103. The superheavy elements are those beyond the actinides in the periodic table; the l ...
s, though the exact location of the center of the valley of stability is model dependent. It is widely believed that an
island of stability exists along the beta stability line for isotopes of elements around
copernicium
Copernicium is a synthetic chemical element with the symbol Cn and atomic number 112. Its known isotopes are extremely radioactive, and have only been created in a laboratory. The most stable known isotope, copernicium-285, has a half-life of ap ...
that are stabilized by
shell
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
** Thin-shell structure
Science Biology
* Seashell, a hard o ...
closures in the region; such isotopes would decay primarily through alpha decay or spontaneous fission.
Beyond the island of stability, various models that correctly predict the known beta-stable isotopes predict anomalies in the beta-stability line that are unobserved in any known nuclides, such as the existence of two beta-stable nuclides with the same odd mass number.
This is a consequence of the fact that a semi-empirical mass formula must consider shell correction and nuclear deformation, which become far more pronounced for heavy nuclides.
Beta decay toward minimum mass
Beta decay generally causes isotopes to decay toward the isobar with the lowest mass (which is often, but not always, the one with highest binding energy) with the same mass number, those not in italics in the table above. Thus, those with lower
atomic number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
and higher
neutron number
The neutron number, symbol ''N'', is the number of neutrons in a nuclide.
Atomic number (proton number) plus neutron number equals mass number: . The difference between the neutron number and the atomic number is known as the neutron excess: . ...
than the minimum-mass isobar undergo
beta-minus decay, while those with higher atomic number and lower neutron number undergo
beta-plus decay or
electron capture
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. Thi ...
. However, there are four nuclides that are exceptions, in that the majority of their decays are in the opposite direction:
Notes
References
External links
* Decay-Chains https://www-nds.iaea.org/relnsd/NdsEnsdf/masschain.html
* (Russian
Beta-decay stable nuclides up to ''Z''=118
{{DEFAULTSORT:Beta-Decay Stable Isobars
Nuclear physics