Aluminium or aluminum (13Al) has 22 known isotopes from 22Al to 43Al 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. The standard atomic weight is 26.9815385(7). 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]

Main isotopes of aluminium (13Al)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
26Al trace 7.17×105 y β+ 26Mg
ε 26Mg
γ
27Al 100% stable
Standard atomic weight Ar, standard(Al)
  • 26.9815385(7)[1]

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.[2]

Contents

List of isotopesEdit

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)[3]
 
half-life decay
mode(s)[4][n 1]
daughter
isotope(s)[n 2]
nuclear
spin and
parity
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
excitation energy
22Al 13 9 22.01954(43)# 91.1(5) ms β+, p (55%) 21Na (4)+
β+ (43.862%) 22Mg
β+, 2p (1.1%) 20Ne
β+, α (0.038%) 21Na
23Al 13 10 23.0072444(4) 470(30) ms β+ (99.54%) 23Mg 5/2+
β+, p (0.46%) 22Na
24Al 13 11 23.99994754(25) 2.053(4) s β+ (99.9634%) 24Mg 4+
β+, α (.035%) 20Ne
β+, p (.0016%) 23Na
24mAl 425.8(1) keV 130(3) ms IT (82.5%) 24Al 1+
β+ (17.5%) 24Mg
β+, α (.028%) 20Ne
25Al 13 12 24.99042831(7) 7.183(12) s β+ 25Mg 5/2+
26Al[n 3] 13 13 25.98689186(7) 7.17(24)×105 years β+ 26Mg 5+ Trace[n 4]
26mAl 228.306(13) keV 6.3460(8) s β+ 26Mg 0+
27Al 13 14 26.98153841(5) Stable 5/2+ 1.0000
28Al 13 15 27.98191009(8) 2.245(5) min β 28Si 3+
29Al 13 16 28.9804532(4) 6.56(6) min β 29Si 5/2+
30Al 13 17 29.982968(3) 3.62(6) s β 30Si 3+
31Al 13 18 30.9839498(24) 644(25) ms β (98.4%) 31Si 5/2(+)
β, n (1.6%) 30Si
32Al 13 19 31.988084(8) 33.0(2) ms β (99.3%) 32Si 1+
β, n (.7%) 31Si
32mAl 955.7(4) keV 200(20) ns IT 32Al (4+)
33Al 13 20 32.990878(8) 41.7(2) ms β (91.5%) 33Si 5/2+
β, n (8.5%) 32Si
34Al 13 21 33.996779(3) 56.3(5) ms β (74%) 34Si (4−)
β, n (26%) 33Si
34mAl 550(100)# keV 26(1) ms β (70%) 34Si (1+)
β, n (30%) 33Si
35Al 13 22 34.999760(8) 37.2(8) ms β (62%) 35Si 5/2+#
β, n (38%) 34Si
36Al 13 23 36.00639(16) 90(40) ms β (70%) 36Si
β, n (30%) 35Si
37Al 13 24 37.01053(19) 11.5(4) ms β (71%) 37Si 5/2+#
β, n (29%) 36Si
38Al 13 25 38.0174(4) 9.0(7) ms β 38Si
39Al 13 26 39.02217(43)# 7.6(16) ms β, n (90%) 38Si 5/2+#
β (10%) 39Si
40Al 13 27 40.02962(43)# 10# ms [>260 ns] β 40Si
41Al 13 28 41.03588(54)# 2# ms [>260 ns] β 41Si 5/2+#
42Al 13 29 42.04305(64)# 1# ms [>170 ns] β 42Si
43Al 13 30 43.05048(86)# 1# ms [>170 ns] β 42Si
  1. ^ Abbreviations:
    IT: Isomeric transition
  2. ^ Bold for stable isotopes
  3. ^ Used in radiodating events early in the Solar System's history and meteorites
  4. ^ cosmogenic

NotesEdit

  • 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 alsoEdit

ReferencesEdit

  • Isotope masses from:
    • Audi, Georges; Bersillon, Olivier; Blachot, Jean; Wapstra, Aaldert Hendrik (2003), "The NUBASE evaluation of nuclear and decay properties", 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:
  1. ^ Meija, Juris; 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. ^ R. T. Dodd (1986). Thunderstones and Shooting Stars. pp. 89–90. ISBN 978-0-674-89137-1.
  3. ^ Wang, Meng; Audi, Georges; Kondev, Filip G.; Huang, Wen Jian; Naimi, Sarah; Xu, Xing (2017), "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF), Chinese Physics C, 41 (3): 030003–1—030003–442, doi:10.1088/1674-1137/41/3/030003
  4. ^ Audi, Georges; Kondev, Filip G.; Wang, Meng; Huang, Wen Jia; Naimi, Sarah (2017), "The NUBASE2016 evaluation of nuclear properties" (PDF), Chinese Physics C, 41 (3): 030001–1—030001–138, Bibcode:2017ChPhC..41c0001A, doi:10.1088/1674-1137/41/3/030001

External linksEdit