Isotopes of aluminium
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Aluminium or aluminum (13Al) has one stable isotope, 27Al, comprising all natural aluminium. The radioactive 26Al, with half-life 717,000 years, occurs in traces from cosmic-ray spallation of argon in the atmosphere.
Other than 26Al, there are 22 known synthetic radioisotopes from 20Al to 43Al, and 4 known metastable states; all have half-lives under 7 minutes, most under a second.
26Al is an extinct radionuclide and has received attention as such, being used in the study of meteorites. Its terrestrial occurrence has also found practical application in dating marine sediments, manganese nodules, glacial ice, quartz in rock exposures, and meteorites. 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.[4]
List of isotopes
| Nuclide [n 1] |
Z | N | Isotopic mass (Da)[5] [n 2][n 3] |
Discovery year[6][7] |
Half-life[1] |
Decay mode[1] [n 4] |
Daughter isotope [n 5] |
Spin and parity[1] [n 6][n 7] |
Isotopic abundance | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Excitation energy[n 7] | |||||||||||||||||||
| 20Al[8] | 13 | 7 | 20.04326(13) | 2025 | >1.1 zs | p | 19Mg | (1−) | |||||||||||
| 21Al[9] | 13 | 8 | 21.0278(13) | 2024 | >1.1 zs | p | 20Mg | (5/2+) | |||||||||||
| 22Al | 13 | 9 | 22.01942310(32)[10] | 1982 | 91.1(5) ms | β+, p (55%) | 21Na | (4)+ | |||||||||||
| β+ (44%) | 22Mg | ||||||||||||||||||
| β+, 2p (1.10%) | 20Ne | ||||||||||||||||||
| β+, α (0.038%) | 18Ne | ||||||||||||||||||
| 23Al | 13 | 10 | 23.00724435(37) | 1969 | 446(6) ms | β+ (98.78%) | 23Mg | 5/2+ | |||||||||||
| β+, p (1.22%) | 22Na | ||||||||||||||||||
| 24Al | 13 | 11 | 23.99994760(24) | 1953 | 2.053(4) s | β+ (99.96%) | 24Mg | 4+ | |||||||||||
| β+, α (0.035%) | 20Ne | ||||||||||||||||||
| β+, p (0.0016%) | 23Na | ||||||||||||||||||
| 24mAl | 425.8(1) keV | 1966 | 130(3) ms | IT (82.5%) | 24Al | 1+ | |||||||||||||
| β+ (17.5%) | 24Mg | ||||||||||||||||||
| β+, α (0.028%) | 20Ne | ||||||||||||||||||
| 25Al | 13 | 12 | 24.990428308(69) | 1953 | 7.1666(23) s | β+ | 25Mg | 5/2+ | |||||||||||
| 26Al[n 8] | 13 | 13 | 25.986891876(71) | 1934 | 7.17(24)×105 y | β+ (85%) | 26Mg | 5+ | Trace[n 9] | ||||||||||
| EC (15%)[11] | |||||||||||||||||||
| 26mAl | 228.306(13) keV | 1954 | 6.3460(5) s | β+ | 26Mg | 0+ | |||||||||||||
| 27Al | 13 | 14 | 26.981538408(50) | 1922 | Stable | 5/2+ | 1.0000 | ||||||||||||
| 28Al | 13 | 15 | 27.981910009(52) | 1934 | 2.245(5) min | β− | 28Si | 3+ | |||||||||||
| 29Al | 13 | 16 | 28.98045316(37) | 1939 | 6.56(6) min | β− | 29Si | 5/2+ | |||||||||||
| 30Al | 13 | 17 | 29.9829692(21) | 1961 | 3.62(6) s | β− | 30Si | 3+ | |||||||||||
| 31Al | 13 | 18 | 30.9839498(24) | 1971 | 644(25) ms | β− (>98.4%) | 31Si | 5/2+ | |||||||||||
| β−, n (<1.6%) | 30Si | ||||||||||||||||||
| 32Al | 13 | 19 | 31.9880843(77) | 1971 | 32.6(5) ms | β− (99.3%) | 32Si | 1+ | |||||||||||
| β−, n (0.7%) | 31Si | ||||||||||||||||||
| 32mAl | 956.6(5) keV | 1996 | 200(20) ns | IT | 32Al | (4+) | |||||||||||||
| 33Al | 13 | 20 | 32.9908777(75) | 1971 | 41.46(9) ms | β− (91.5%) | 33Si | 5/2+ | |||||||||||
| β−, n (8.5%) | 32Si | ||||||||||||||||||
| 34Al | 13 | 21 | 33.9967819(23) | 1977 | 53.73(13) ms | β− (74%) | 34Si | 4− | |||||||||||
| β−, n (26%) | 33Si | ||||||||||||||||||
| 34mAl | 46.4(17) keV | 2012 | 22.1(2) ms | β− (89%) | 34Si | 1+ | |||||||||||||
| β−, n (11%) | 33Si | ||||||||||||||||||
| 35Al | 13 | 22 | 34.9997598(79) | 1979 | 38.16(21) ms | β− (64.2%) | 35Si | (5/2+,3/2+) | |||||||||||
| β−, n (35.8%) | 34Si | ||||||||||||||||||
| 36Al | 13 | 23 | 36.00639(16) | 1979 | 90(40) ms | β− (>69%) | 36Si | ||||||||||||
| β−, n (<31%) | 35Si | ||||||||||||||||||
| 37Al | 13 | 24 | 37.01053(19) | 1979 | 11.4(3) ms | β−, n (52%) | 36Si | 5/2+# | |||||||||||
| β− (<47%) | 37Si | ||||||||||||||||||
| β−, 2n (>1%) | 35Si | ||||||||||||||||||
| 38Al | 13 | 25 | 38.01768(16)# | 1989 | 9.0(7) ms | β−, n (84%) | 37Si | 0−# | |||||||||||
| β− (16%) | 38Si | ||||||||||||||||||
| 39Al | 13 | 26 | 39.02307(32)# | 1989 | 7.6(16) ms | β−, n (97%) | 38Si | 5/2+# | |||||||||||
| β− (3%) | 39Si | ||||||||||||||||||
| 40Al | 13 | 27 | 40.03094(32)# | 2002 | 5.7(3 (stat), 2 (sys)) ms[12] | β−, n (64%) | 39Si | ||||||||||||
| β−, 2n (20%) | 38Si | ||||||||||||||||||
| β− (16%) | 40Si | ||||||||||||||||||
| 41Al | 13 | 28 | 41.03713(43)# | 2002 | 3.5(8 (stat), 4 (sys)) ms[12] | β−, n (86%) | 40Si | 5/2+# | |||||||||||
| β−, 2n (11%) | 39Si | ||||||||||||||||||
| β− (3%) | 41Si | ||||||||||||||||||
| 42Al | 13 | 29 | 42.04508(54)# | 2007 | 3# ms [>170 ns] |
||||||||||||||
| 43Al | 13 | 30 | 43.05182(64)# | 2007 | 4# ms [>170 ns] |
β−? | 43Si | 5/2+# | |||||||||||
| This table header & footer: | |||||||||||||||||||
- mAl – Excited nuclear isomer.
- ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
- Modes of decay:
IT: Isomeric transition - Bold symbol as daughter – Daughter product is stable.
- ( ) spin value – Indicates spin with weak assignment arguments.
- # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- Used in radiodating events early in the Solar System's history and meteorites
Aluminium-26
Cosmogenic aluminium-26 was first described 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.[15]
See also
Daughter products other than aluminum