Isotopes of aluminium
Encyclopedia
Aluminium
(Al) has 22 known isotope
s from 21Al to 42Al and 4 known isomers
. Only 27Al (stable isotope
) and 26Al (radioactive
isotope, t1/2 = 7.2 × 105 y
) occur naturally, however 27Al has a natural abundance of 99.9+ %. Other than 26Al, all radioisotopes have half-lives under 7 minutes, most under a second. Standard atomic mass is 26.9815386(8) u. 26Al is produced from argon
in the atmosphere
by spallation
caused by cosmic-ray proton
s. Aluminium isotopes have found practical application in dating marine
sediment
s, manganese nodule
s, glacial ice, quartz
in rock
exposures, and meteorite
s. The ratio of 26Al to 10Be
has been used to study the role of sediment transport
, deposition
, and storage, as well as burial times, and erosion, on 105 to 106 year time scales.
Cosmogenic Aluminium-26
was first applied in studies of the Moon
and meteorites. Meteorite fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial 26Al production. After falling to Earth, atmospheric shielding protects the meteorite fragments from further 26Al production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. Most meteoriticists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation
of some asteroids after their formation 4.55 billion years ago.
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
(Al) has 22 known isotope
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...
s from 21Al to 42Al and 4 known isomers
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
. Only 27Al (stable isotope
Stable isotope
Stable isotopes are chemical isotopes that may or may not be radioactive, but if radioactive, have half-lives too long to be measured.Only 90 nuclides from the first 40 elements are energetically stable to any kind of decay save proton decay, in theory...
) and 26Al (radioactive
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
isotope, t1/2 = 7.2 × 105 y
Year
A year is the orbital period of the Earth moving around the Sun. For an observer on Earth, this corresponds to the period it takes the Sun to complete one course throughout the zodiac along the ecliptic....
) occur naturally, however 27Al has a natural abundance of 99.9+ %. Other than 26Al, all radioisotopes have half-lives under 7 minutes, most under a second. Standard atomic mass is 26.9815386(8) u. 26Al is produced from argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
in the atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
by spallation
Spallation
In general, spallation is a process in which fragments of material are ejected from a body due to impact or stress. In the context of impact mechanics it describes ejection or vaporization of material from a target during impact by a projectile...
caused by cosmic-ray proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
s. Aluminium isotopes have found practical application in dating marine
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
sediment
Sediment
Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....
s, manganese nodule
Manganese nodule
Polymetallic nodules, also called manganese nodules, are rock concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. The core may be microscopically small and is sometimes completely transformed into manganese minerals by crystallization...
s, glacial ice, quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
in rock
Rock (geology)
In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...
exposures, and meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
s. The ratio of 26Al to 10Be
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
has been used to study the role of sediment transport
Sediment transport
Sediment transport is the movement of solid particles , typically due to a combination of the force of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained...
, deposition
Deposition (geology)
Deposition is the geological process by which material is added to a landform or land mass. Fluids such as wind and water, as well as sediment flowing via gravity, transport previously eroded sediment, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of...
, and storage, as well as burial times, and erosion, on 105 to 106 year time scales.
Cosmogenic Aluminium-26
Aluminium-26
Aluminium-26, 26Al, is a radioactive isotope of the chemical element aluminium, decaying by either of the modes beta-plus or electron capture, both resulting in the stable nuclide magnesium-26. The half-life of 26Al is 7.17 years...
was first applied in studies of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
and meteorites. Meteorite fragments, after departure from their parent bodies, are exposed to intense cosmic-ray bombardment during their travel through space, causing substantial 26Al production. After falling to Earth, atmospheric shielding protects the meteorite fragments from further 26Al production, and its decay can then be used to determine the meteorite's terrestrial age. Meteorite research has also shown that 26Al was relatively abundant at the time of formation of our planetary system. Most meteoriticists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation
Planetary differentiation
In planetary science, planetary differentiation is the process of separating out different constituents of a planetary body as a consequence of their physical or chemical behaviour, where the body develops into compositionally distinct layers; the denser materials of a planet sink to the center,...
of some asteroids after their formation 4.55 billion years ago.
Table
| nuclide symbol |
Z(p Proton The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.... ) |
N(n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... ) |
isotopic mass (u) |
half-life | decay mode(s)Abbreviations: IT: Isomeric transition Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... |
daughter isotope(s)Bold for stable isotopes |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|
| excitation energy | |||||||||
| 21Al | 13 | 8 | 21.02804(32)# | <35 ns | p Proton decay In particle physics, proton decay is a hypothetical form of radioactive decay in which the proton decays into lighter subatomic particles, such as a neutral pion and a positron... |
20Mg | 1/2+# | ||
| 22Al | 13 | 9 | 22.01952(10)# | 59(3) ms | 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... (96.7%) |
22Mg | (3)+ | ||
| β+, 2p (2.5%) | 20Ne | ||||||||
| β+, p (0.8%) | 21Na | ||||||||
| 23Al | 13 | 10 | 23.007267(20) | 470(30) ms | β+ (92%) | 23Mg | 5/2+# | ||
| β+, p (8%) | 22Na | ||||||||
| 23mAl | ~0.35 s | #79 | |||||||
| 24Al | 13 | 11 | 23.9999389(30) | 2.053(4) s | β+ (99.95%) | 24Mg | 4+ | ||
| β+, α 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... (.0349%) |
20Ne | ||||||||
| β+, p (.0159%) | 23Na | ||||||||
| 24mAl | 425.8(1) keV | 131.3(25) ms | IT Isomeric transition An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.... (82%) |
24Al | 1+ | ||||
| β+ (18%) | 24Mg | ||||||||
| β+, α | 20Ne | ||||||||
| 25Al | 13 | 12 | 24.9904281(5) | 7.183(12) s | β+ | 25Mg | 5/2+ | ||
| 26Al Aluminium-26 Aluminium-26, 26Al, is a radioactive isotope of the chemical element aluminium, decaying by either of the modes beta-plus or electron capture, both resulting in the stable nuclide magnesium-26. The half-life of 26Al is 7.17 years... Used in radiodating events early in the Solar System's history and meteorite Meteorite A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids... s |
13 | 13 | 25.98689169(6) | 7.17(24)×105 a | β+ | 26Mg | 5+ | Tracecosmogenic Cosmogenic nuclide See also Environmental radioactivity#NaturalCosmogenic nuclides are rare isotopes created when a high-energy cosmic ray interacts with the nucleus of an in situ solar system atom, causing cosmic ray spallation... |
|
| 26mAl | 228.305(13) keV | 6.3452(19) s | β+ | 26Mg | 0+ | ||||
| 27Al | 13 | 14 | 26.98153863(12) | STABLE | 5/2+ | 1.0000 | |||
| 28Al | 13 | 15 | 27.98191031(14) | 2.2414(12) min | β- | 28Si | 3+ | ||
| 29Al | 13 | 16 | 28.9804450(13) | 6.56(6) min | β- | 29Si | 5/2+ | ||
| 30Al | 13 | 17 | 29.982960(15) | 3.60(6) s | β- | 30Si | 3+ | ||
| 31Al | 13 | 18 | 30.983947(22) | 644(25) ms | β- (98.4%) | 31Si | (3/2,5/2)+ | ||
| β-, n Neutron emission Neutron emission is a type of radioactive decay of atoms containing excess neutrons, in which a neutron is simply ejected from the nucleus. Two examples of isotopes which emit neutrons are helium-5 and beryllium-13... (1.6%) |
30Si | ||||||||
| 32Al | 13 | 19 | 31.98812(9) | 31.7(8) ms | β- (99.3%) | 32Si | 1+ | ||
| β-, n (.7%) | 31Si | ||||||||
| 32mAl | 955.7(4) keV | 200(20) ns | (4+) | ||||||
| 33Al | 13 | 20 | 32.99084(8) | 41.7(2) ms | β- (91.5%) | 33Si | (5/2+)# | ||
| β-, n (8.5%) | 32Si | ||||||||
| 34Al | 13 | 21 | 33.99685(12) | 56.3(5) ms | β- (87.5%) | 34Si | 4-# | ||
| β-, n (12.5%) | 33Si | ||||||||
| 35Al | 13 | 22 | 34.99986(19) | 38.6(4) ms | β- (74%) | 35Si | 5/2+# | ||
| β-, n (26%) | 33Si | ||||||||
| 36Al | 13 | 23 | 36.00621(23) | 90(40) ms | β- (69%) | 36Si | |||
| β-, n (31%) | 35Si | ||||||||
| 37Al | 13 | 24 | 37.01068(36) | 10.7(13) ms | β- | 37Si | 3/2+ | ||
| 38Al | 13 | 25 | 38.01723(78) | 7.6(6) ms | β- | 38Si | |||
| 39Al | 13 | 26 | 39.02297(158) | 7.6(16) ms | β- | 39Si | 3/2+# | ||
| 40Al | 13 | 27 | 40.03145(75)# | 10# ms [>260 ns] | |||||
| 41Al | 13 | 28 | 41.03833(86)# | 2# ms [>260 ns] | 3/2+# | ||||
| 42Al | 13 | 29 | 42.04689(97)# | 1 ms | |||||