Isotopes of magnesium

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Magnesium (Mg) naturally occurs in three stable isotopes, 24Mg, 25Mg, and 26Mg. 19 radioisotopes 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 39Mg with a half-life shorter than 180 nanoseconds, or possibly 40Mg, with a half-life longer than 170 nanoseconds (the half-life of 19Mg is unknown).

Standard atomic mass: 24.3050(6) u

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

Table[edit]

nuclide
symbol
proton neutron  
isotopic mass (u)
 
half-life decay mode(s)[1] daughter
isotope(s)[n 1]
nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
19Mg 12 7 19.03547(27) 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 3/2+
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 7/2-#
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

References[edit]

External links[edit]

  1. ^ http://www.nucleonica.net/unc.aspx


Isotopes of sodium Isotopes of magnesium Isotopes of aluminium
Table of nuclides