Isotopes of magnesium
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Magnesium (12Mg) naturally occurs as three stable isotopes: 24
Mg, 25
Mg, and 26
Mg. There are also 19 artificial radioisotopes that have been discovered, ranging from 18
Mg to 40
Mg (with the exception of 39
Mg). The longest-lived of them is 28
Mg with a half-life of 20.915 hours. The isotopes lighter than the stable ones mostly decay to isotopes of sodium, while those heavier decay to isotopes of aluminium.
A precise measurement of the neutron-rich 40Mg in 2019 showed an unexpected difference in its nuclear structure, compared to the lighter neighboring isotopes.[4][5]
List of isotopes
| Nuclide |
Z | N | Isotopic mass (Da)[6] [n 1] |
Half-life[1] [n 2] |
Decay mode[1] [n 3] |
Daughter isotope [n 4] |
Spin and parity[1] [n 5][n 2] |
Natural abundance (mole fraction) | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Normal proportion[1] | Range of variation | ||||||||||||||||||
| 18 Mg[7] |
12 | 6 | 4.0(3.4) zs | 2p | 16 Ne[n 6] |
0+ | |||||||||||||
| 19 Mg |
12 | 7 | 19.034180(60) | 5(3) ps | 2p | 17 Ne |
1/2−# | ||||||||||||
| 20 Mg |
12 | 8 | 20.0187631(20) | 90.4(5) ms | β+ (69.7(1.2)%) | 20 Na |
0+ | ||||||||||||
| β+p (30.3(1.2)%) | 19 Ne | ||||||||||||||||||
| 21 Mg |
12 | 9 | 21.0117058(8) | 120.0(4) ms | β+ (79.8(2.1)%) | 21 Na |
5/2+ | ||||||||||||
| β+p (20.1(2.1)%) | 20 Ne | ||||||||||||||||||
| β+α (0.116(18)%) | 17 F | ||||||||||||||||||
| β+pα (0.016(3)%) | 16 O | ||||||||||||||||||
| 22 Mg |
12 | 10 | 21.99957060(17) | 3.8745(7) s | β+ | 22 Na |
0+ | ||||||||||||
| 23 Mg |
12 | 11 | 22.99412377(3) | 11.3039(32) s | β+ | 23 Na |
3/2+ | ||||||||||||
| 24 Mg |
12 | 12 | 23.985041689(14) | Stable | 0+ | [0.7888, 0.7905] | |||||||||||||
| 25 Mg |
12 | 13 | 24.98583697(5) | Stable | 5/2+ | [0.09988, 0.10034] | |||||||||||||
| 26 Mg[n 7] |
12 | 14 | 25.98259297(3) | Stable | 0+ | [0.1096, 0.1109] | |||||||||||||
| 27 Mg |
12 | 15 | 26.98434065(5) | 9.435(27) min | β− | 27 Al |
1/2+ | ||||||||||||
| 28 Mg |
12 | 16 | 27.98387543(28) | 20.915(9) h | β− | 28 Al |
0+ | ||||||||||||
| 29 Mg |
12 | 17 | 28.9886072(4) | 1.30(12) s | β− | 29 Al |
3/2+ | ||||||||||||
| 30 Mg |
12 | 18 | 29.9904655(14) | 317(4) ms | β− (> 99.94%) | 30 Al |
0+ | ||||||||||||
| β−n (< 0.06%) | 29 Al | ||||||||||||||||||
| 31 Mg |
12 | 19 | 30.996648(3) | 270(2) ms | β− (93.8(1.9)%) | 31 Al |
1/2+ | ||||||||||||
| β−n (6.2(1.9)%) | 30 Al | ||||||||||||||||||
| 32 Mg |
12 | 20 | 31.999110(4) | 80.4(4) ms | β− (94.5(5)%) | 32 Al |
0+ | ||||||||||||
| β−n (5.5(5)%) | 31 Al | ||||||||||||||||||
| 33 Mg |
12 | 21 | 33.0053279(29) | 92.0(1.2) ms | β− (86(2)%) | 33 Al |
3/2− | ||||||||||||
| β−n (14(2)%) | 32 Al | ||||||||||||||||||
| β−2n ? | 31 Al ? | ||||||||||||||||||
| 34 Mg |
12 | 22 | 34.008935(7) | 44.9(4) ms | β− (> 78.9(7.0)%) | 34 Al |
0+ | ||||||||||||
| β−n (21(7)%) | 33 Al | ||||||||||||||||||
| β−2n (< 0.1%) | 32 Al | ||||||||||||||||||
| 35 Mg |
12 | 23 | 35.01679(29) | 11.3(6) ms | β−n (52(46)%) | 34 Al |
(3/2−, 5/2−) | ||||||||||||
| β− (48(46)%) | 35 Al | ||||||||||||||||||
| β−2n ? | 33 Al ? | ||||||||||||||||||
| 36 Mg |
12 | 24 | 36.02188(74) | 3.9(1.3) ms | β− (52(12)%) | 36 Al |
0+ | ||||||||||||
| β−n (48(12)%) | 35 Al | ||||||||||||||||||
| β−2n ? | 34 Al ? | ||||||||||||||||||
| 37 Mg |
12 | 25 | 37.03029(75) | 8(4) ms | β− ? | 37 Al ? |
(3/2−) | ||||||||||||
| β−n ? | 36 Al ? | ||||||||||||||||||
| β−2n ? | 35 Al ? | ||||||||||||||||||
| 38 Mg |
12 | 26 | 38.03658(54)# | 3.1(4 (stat), 2 (sys)) ms[8] | β−n (81%) | 37 Al |
0+ | ||||||||||||
| β− (9%) | 38 Al | ||||||||||||||||||
| β−2n (9%) | 36 Al | ||||||||||||||||||
| 40 Mg |
12 | 28 | 40.05319(54)# | 1# ms [> 170 ns] | β− ? | 40 Al ? |
0+ | ||||||||||||
| β−n ? | 39 Al ? | ||||||||||||||||||
| β−2n ? | 38 Al ? | ||||||||||||||||||
| This table header & footer: | |||||||||||||||||||
- ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
- Modes of decay:
n: Neutron emission p: Proton emission - Bold symbol as daughter – Daughter product is stable.
- ( ) spin value – Indicates spin with weak assignment arguments.
- Also immediately emits two protons for the net reaction of 18Mg -> 14O + 4 1H
- Used in radiodating events early in the Solar System's history, as product of the extinct 26Al
See also
Daughter products other than magnesium