Isotopes of magnesium

Magnesium (12Mg) naturally occurs in three stable isotopes, 24Mg, 25Mg, and 26Mg. There are 18 radioisotopes that have been discovered, ranging from 19Mg to 40Mg. The longest-lived radioisotope is 28Mg with a half-life of 20.915 hours. The lighter isotopes mostly decay to isotopes of sodium while the heavier isotopes decay to isotopes of aluminium. The shortest-lived is 19Mg with a half-life of 5 picoseconds.

The abundances of the naturally occurring isotopes of magnesium.
Main isotopes of magnesium (12Mg)
Iso­tope Decay
abun­dance half-life (t1/2) mode pro­duct
24Mg 79.0% stable
25Mg 10.0% stable
26Mg 11.0% stable
Standard atomic weight Ar, standard(Mg)
  • [24.304, 24.307][1]
  • Conventional: 24.305

List of isotopes

Nuclide[2]
Z N Isotopic mass (Da)[3]
[n 1]
Half-life
[n 2]
Decay
mode

[n 3]
Daughter
isotope

[n 4]
Spin and
parity
[n 5][n 2]
Natural abundance (mole fraction)
Normal proportion Range of variation
19Mg 12 7 19.03417(5) 5(3) ps 2p 17Ne 1/2−#
20Mg 12 8 20.0187631(2) 93(5) ms β+ (69.7%) 20Na 0+
β+, p (30.3%) 19Ne
21Mg 12 9 21.0117058(8) 118.6(5) ms β+ (66.9%) 21Na 5/2+
β+, p (32.6%) 20Ne
β+, α (0.5%) 17F
22Mg 12 10 21.9995707(3) 3.8755(12) s β+ 22Na 0+
23Mg 12 11 22.99412394(17) 11.317(11) s β+ 23Na 3/2+
24Mg 12 12 23.985041697(14) Stable 0+ 0.7899(4) 0.78958–0.79017
25Mg 12 13 24.98583696(5) Stable 5/2+ 0.1000(1) 0.09996–0.10012
26Mg[n 6] 12 14 25.98259297(3) Stable 0+ 0.1101(3) 0.10987–0.11030
27Mg 12 15 26.98434063(5) 9.435(27) min β 27Al 1/2+
28Mg 12 16 27.9838766(21) 20.915(9) h β 28Al 0+
29Mg 12 17 28.988617(12) 1.30(12) s β 29Al 3/2+
30Mg 12 18 29.990463(4) 313(4) ms β (99.94%) 30Al 0+
β, n (0.06%) 29Al
31Mg 12 19 30.996648(3) 236(20) ms β (93.8%) 31Al 1/2(+)
β, n (6.2%) 30Al
32Mg 12 20 31.999110(4) 86(5) ms β (94.5%) 32Al 0+
β, n (5.5%) 31Al
33Mg 12 21 33.005327(3) 90.5(16) ms β (86%) 33Al 3/2−
β, n (14%) 32Al
34Mg 12 22 34.00894(3) 20(10) ms β (70%) 34Al 0+
β, n (30%) 33Al
35Mg 12 23 35.01679(29) 70(40) ms β, n (52%) 34Al 7/2−#
β (48%) 35Al
36Mg 12 24 36.02188(74) 3.9(13) ms β 36Al 0+
37Mg 12 25 37.03029(75) 8(4) ms β 37Al (3/2−)
β, n 36Al
38Mg 12 26 38.03658(54)# 1# ms [>260 ns] 0+
40Mg 12 28 40.05191(54)# 1# ms β, n 39Al 0+
β 40Al
  1. ()  Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
  2. #  Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
  3. Modes of decay:
    n:Neutron emission
    p:Proton emission
  4. Bold symbol as daughter  Daughter product is stable.
  5. () spin value  Indicates spin with weak assignment arguments.
  6. Used in radiodating events early in the Solar System's history

References

  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. Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
    Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
  3. Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (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.
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