Isotopes of aluminium
Aluminium (Al) has 22 known isotopes 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. Relative atomic mass is 26.9815386(8). 26Al is produced from argon in the atmosphere by spallation caused by cosmic-ray protons. Aluminium isotopes have 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.[citation needed]
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.[1]
Table
| nuclide symbol |
Z(p) | N(n) | isotopic mass (u) |
half-life | decay mode(s)[2][n 1] |
daughter isotope(s)[n 2] |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|
| excitation energy | |||||||||
| 19Al | 13 | 6 | 19.0218# | <35 ns | p | 18Mg | |||
| 20Al | 13 | 7 | 20.0194# | <35 ns | p | 19Mg | |||
| 21Al | 13 | 8 | 21.02804(32)# | <35 ns | p | 20Mg | 1/2+# | ||
| 22Al | 13 | 9 | 22.01952(10)# | 59(3) ms | β+ (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 (.0349%) | 20Ne | ||||||||
| β+, p (.0159%) | 23Na | ||||||||
| 24mAl | 425.8(1) keV | 131.3(25) ms | IT (82%) | 24Al | 1+ | ||||
| β+ (18%) | 24Mg | ||||||||
| β+, α | 20Ne | ||||||||
| 25Al | 13 | 12 | 24.9904281(5) | 7.183(12) s | β+ | 25Mg | 5/2+ | ||
| 26Al[n 3] | 13 | 13 | 25.98689169(6) | 7.17(24)×105 years | β+ | 26Mg | 5+ | Trace[n 4] | |
| 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 (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%) | 34Si | ||||||||
| 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 | |||||
- ^ Abbreviations:
IT: Isomeric transition - ^ Bold for stable isotopes
- ^ Used in radiodating events early in the Solar System's history and meteorites
- ^ cosmogenic
Notes
- Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
- Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC, which use expanded uncertainties.
See also
References
- Isotope masses from:
- G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
- Isotopic compositions and standard atomic masses from:
- J. R. de Laeter; J. K. Böhlke; P. De Bièvre; H. Hidaka; H. S. Peiser; K. J. R. Rosman; P. D. P. Taylor (2003). "Atomic weights of the elements. Review 2000 (IUPAC Technical Report)". Pure and Applied Chemistry. 75 (6): 683–800. doi:10.1351/pac200375060683.
- M. E. Wieser (2006). "Atomic weights of the elements 2005 (IUPAC Technical Report)". Pure and Applied Chemistry. 78 (11): 2051–2066. doi:10.1351/pac200678112051.
{{cite journal}}: Unknown parameter|laysummary=ignored (help) - G. Audi; A. H. Wapstra; C. Thibault; J. Blachot; O. Bersillon (2003). "The NUBASE evaluation of nuclear and decay properties" (PDF). Nuclear Physics A. 729: 3–128. Bibcode:2003NuPhA.729....3A. doi:10.1016/j.nuclphysa.2003.11.001.
- National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005.
{{cite web}}: Check date values in:|accessdate=(help) - N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide (ed.). CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.
{{cite book}}: Unknown parameter|nopp=ignored (|no-pp=suggested) (help)
- ^ R. T. Dodd. Thunderstones and Shooting Stars. pp. 89–90. ISBN 0-674-89137-6.
- ^ "Universal Nuclide Chart". Nucleonica. Retrieved 2012-08-15.
{{cite web}}: Unknown parameter|registration=ignored (|url-access=suggested) (help)
External links
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