Isotopes of aluminium

Main isotopes of Chemistry:aluminium (13Al) | Iso­tope | Decay

|

| abun­dance | half-life (t1/2) | mode | pro­duct
26Al  | trace | 7.17×105 y  | β+ (85%)  | 26Mg
ε (15%)  | 26Mg
γ | –
27Al  | 100%  | stable
Standard atomic weight Ar, standard(Al)|

* 26.9815385(7)[1]

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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.[2]

## Contents

* 1 List of isotopes
* 2 Aluminium-26
* 3 See also
* 4 References

## List of isotopes

Nuclide
[n 1] | Z | N | Isotopic mass (u)
[n 2][n 3] | Half-life
| Decay
mode
[n 4] | Daughter
isotope
[n 5] | Spin and
parity
[n 6][n 7] | Physics:Natural abundance (mole fraction)

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Excitation energy[n 7] | Normal proportion  | Range of variation
20Al[3] | 13  | 7  | 20.04326(13)  | 2025 | >1.1 zs  | p  | 19Mg  | (1−)  |
21Al[4] | 13  | 8  | 21.0278(13)  | 2024 | >1.1 zs  | p  | 20Mg  | (5/2+)  |
22Al  | 13  | 9  | 22.01942310(32)[5] | 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%)[6]
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[7] | 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[7] | 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+#  |

1. ↑ mAl - Excited nuclear isomer.
2. ↑ ( ) - Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. ↑ # - Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. ↑ Modes of decay:  IT: | Isomeric transition

|

5. ↑ Bold symbol as daughter - Daughter product is stable.
6. ↑ ( ) spin value - Indicates spin with weak assignment arguments.
7. ↑ 7.0 7.1 # - Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
8. ↑ Used in radiodating events early in the Solar System's history and meteorites
9. ↑ cosmogenic

## Aluminium-26

Main article: Physics:Aluminium-26

The decay level scheme for 26Al and 26mAl to 26Mg.[8][9]

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.[10]

## See also

Daughter products other than aluminum

* Isotopes of silicon
* Isotopes of magnesium
* Isotopes of sodium
* Isotopes of neon

## References

1. ↑ Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry 88 (3): 265–91. doi:10.1515/pac-2015-0305.
2. ↑ Dickin, A.P. (2005). "In situ Cosmogenic Isotopes". Radiogenic Isotope Geology. Cambridge University Press. ISBN 978-0-521-53017-0. http://www.onafarawayday.com/Radiogenic/Ch14/Ch14-6.htm. Retrieved 16 July 2008.
3. ↑ Kostyleva, D. et al. (2025-07-10). "Isospin Symmetry Breaking Disclosed in the Decay of Three-Proton Emitter 20Al". Physical Review Letters 135 (2): 022502. doi:10.1103/hkmy-yfdk. ISSN 0031-9007. PMID 40743202.
4. ↑ Kostyleva, D. et al. (2024-09-03). "Observation and spectroscopy of the proton-unbound nucleus 21Al". Physical Review C 110 (3). doi:10.1103/PhysRevC.110.L031301. ISSN 2469-9985.
5. ↑ Campbell, S. E.; Bollen, G.; Brown, B. A.; Dockery, A.; Ireland, C. M.; Minamisono, K.; Puentes, D.; Rickey, B. J. et al. (9 April 2024). "Precision Mass Measurement of the Proton Dripline Halo Candidate Al 22". Physical Review Letters 132 (15). doi:10.1103/PhysRevLett.132.152501. PMID 38683002.
6. ↑ Mougeot, X. (2019). "Towards high-precision calculation of electron capture decays". Applied Radiation and Isotopes 154 (108884). doi:10.1016/j.apradiso.2019.108884. PMID 31518864. Bibcode: 2019AppRI.15408884M. https://hal-cea.archives-ouvertes.fr/cea-02475843/document.
7. ↑ 7.0 7.1 Crawford, H. L.Expression error: Unrecognized word "et". (2022). "Crossing N = 28 toward the neutron drip line: first measurement of half-lives at FRIB". Physical Review Letters 129 (212501). doi:10.1103/PhysRevLett.129.212501. PMID 36461950. Bibcode: 2022PhRvL.129u2501C.
8. ↑ "Physics 6805 Topics in Nuclear Physics". Ohio State University. https://www.asc.ohio-state.edu/physics/ntg/6805/figures/al26scheme.jpg.
9. ↑ Diehl, R (13 Dec 2005). "26Al in the inner Galaxy". Astronomy & Astrophysics 449 (3): 1025–1031. doi:10.1051/0004-6361:20054301. http://www2011.mpe.mpg.de/gamma/science/lines/26Al/Al26_SPI_A&A2005_astro-ph.pdf. Retrieved 12 June 2019.
10. ↑ R. T. Dodd (1986). Thunderstones and Shooting Stars. Harvard University Press. pp. 89–90. ISBN 978-0-674-89137-1. https://archive.org/details/thunderstonessho00dodd_673.

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