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)
  • [24.304, 24.307][1]
  • Conventional: 24.305

Magnesium (12Mg) naturally occurs in three stable isotopes, 24Mg, 25Mg, and 26Mg. There are 19 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 4 picoseconds.

A chart showing the abundances of the naturally occurring isotopes of magnesium.

List of isotopes

nuclide
symbol		 Z(p) N(n)  
isotopic mass (u)
 		 half-life decay mode(s)[2] daughter
isotope(s)[n 1]		 nuclear
spin and
parity		 representative
isotopic
composition
(mole fraction)		 range of natural
variation
(mole fraction)
19Mg 12 7 19.03547(27) 4×10−12 s 2p 17Ne 1/2−#
20Mg 12 8 20.018863(29) 90.8(24) ms β+ (97%) 20Na 0+
β+, p (3%) 19Ne
21Mg 12 9 21.011713(18) 122(2) ms β+ (66.9%) 21Na (5/2,3/2)+
β+, p (32.6%) 20Ne
β+, α (0.5%) 17F
22Mg 12 10 21.9995738(14) 3.8755(12) s β+ 22Na 0+
23Mg 12 11 22.9941237(14) 11.317(11) s β+ 23Na 3/2+
24Mg 12 12 23.985041700(14) Stable 0+ 0.7899(4) 0.78958–0.79017
25Mg 12 13 24.98583692(3) Stable 5/2+ 0.1000(1) 0.09996–0.10012
26Mg[n 2] 12 14 25.982592929(30) Stable 0+ 0.1101(3) 0.10987–0.11030
27Mg 12 15 26.98434059(5) 9.458(12) min β− 27Al 1/2+
28Mg 12 16 27.9838768(22) 20.915(9) h β− 28Al 0+
29Mg 12 17 28.988600(15) 1.30(12) s β− 29Al 3/2+
30Mg 12 18 29.990434(9) 335(17) ms β− (99.94%) 30Al 0+
β−, n (.06%) 29Al
31Mg 12 19 30.996546(13) 230(20) ms β− (98.3%) 31Al 1/2+
β−, n (1.7%) 30Al
32Mg 12 20 31.998975(19) 86(5) ms β− (97.6%) 32Al 0+
β−, n (2.4%) 31Al
33Mg 12 21 33.005254(21) 90.5(16) ms β− (83%) 33Al 3/2−
β−, n (17%) 32Al
34Mg 12 22 34.00946(25) 20(10) ms β− (>99.9%) 34Al 0+
β−, n (<.1%) 33Al
35Mg 12 23 35.01734(43)# 70(40) ms β−, n (52%) 34Al (7/2−)#
β− (48%) 35Al
36Mg 12 24 36.02300(54)# 3.9(13) ms β− 36Al 0+
37Mg 12 25 37.03140(97)# 40# ms [>260 ns] β− 37Al 7/2−#
β−, n 36Al
38Mg 12 26 38.03757(54)# 1# ms [>260 ns] 0+
39Mg 12 27 39.04677(55)# <260 ns 7/2−#
40Mg 12 28 40.05393(97)# 1# ms 0+
  1. ↑ Bold for stable isotopes
  2. ↑ Used in radiodating events early in the Solar System's history

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.

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. Archived from the original (PDF) on 2008-09-23.
  • 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. Lay summary.
  • Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.
    • 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. Archived from the original (PDF) on 2008-09-23.
    • National Nuclear Data Center. "NuDat 2.1 database". Brookhaven National Laboratory. Retrieved September 2005. Check date values in: |accessdate= (help)
    • N. E. Holden (2004). "Table of the Isotopes". In D. R. Lide. CRC Handbook of Chemistry and Physics (85th ed.). CRC Press. Section 11. ISBN 978-0-8493-0485-9.
  1. ↑ Meija, J.; 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. ↑ "Universal Nuclide Chart". nucleonica. (Registration required (help)).
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