Magnesium (12 Mg) naturally occurs in three stable isotopes: 24 Mg , 25 Mg , and 26 Mg . There are 19 radioisotopes that have been discovered, ranging from 18 Mg to 40 Mg (with the exception of 39 Mg ). The longest-lived radioisotope is 28 Mg with a half-life of 20.915(9) h . The lighter isotopes mostly decay to isotopes of sodium while the heavier isotopes decay to isotopes of aluminium . The shortest-lived is proton-unbound 18 Mg with a half-life of 4.0(3.4) zeptoseconds .
A precise measurement of the neutron-rich 40 Mg in 2019 showed the unexpected difference in its nuclear structure, compared to the lighter neighboring isotopes.[ 4] [ 5]
The abundances of the naturally occurring isotopes of magnesium.
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 andparity [ 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
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
21.999570 60 (17)
3.8745(7) s
β+
22 Na
0+
23 Mg
12
11
22.994123 77 (3)
11.3039(32) s
β+
23 Na
3/2+
24 Mg
12
12
23.985041 689 (14)
Stable
0+
[ 0.7888 , 0.7905 ]
25 Mg
12
13
24.985836 97 (5)
Stable
5/2+
[ 0.09988 , 0.10034 ]
26 Mg[ n 6]
12
14
25.982592 97 (3)
Stable
0+
[ 0.1096 , 0.1109 ]
27 Mg
12
15
26.984340 65 (5)
9.435(27) min
β−
27 Al
1/2+
28 Mg
12
16
27.983875 43 (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 ?[ n 7]
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 ?[ n 7]
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 ?[ n 7]
34 Al ?
37 Mg
12
25
37.03029 (75)
8(4) ms
β− ?[ n 7]
37 Al ?
(3/2−)
β− n ?[ n 7]
36 Al ?
β− 2n ?[ n 7]
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− ?[ n 7]
40 Al ?
0+
β− n ?[ n 7]
39 Al ?
β− 2n ?[ n 7]
38 Al ?
This table header & footer:
^ ( ) – Uncertainty (1σ ) is given in concise form in parentheses after the corresponding last digits.
^ a b # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
^
Modes of decay:
^ Bold symbol as daughter – Daughter product is stable.
^ ( ) spin value – Indicates spin with weak assignment arguments.
^ Used in radiodating events early in the Solar System's history
^ a b c d e f g h i Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.
External links
References
^ a b c d e Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S.; Audi, G. (2021). "The NUBASE2020 evaluation of nuclear properties" (PDF) . Chinese Physics C . 45 (3): 030001. doi :10.1088/1674-1137/abddae .
^ "Standard Atomic Weights: Magnesium" . CIAAW . 2011.
^ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; Böhlke, John K.; Chesson, Lesley A.; Coplen, Tyler B.; Ding, Tiping; Dunn, Philip J. H.; Gröning, Manfred; Holden, Norman E.; Meijer, Harro A. J. (2022-05-04). "Standard atomic weights of the elements 2021 (IUPAC Technical Report)" . Pure and Applied Chemistry . doi :10.1515/pac-2019-0603 . ISSN 1365-3075 .
^ glennroberts (2019-02-07). "New Measurements of Exotic Magnesium Suggest Surprising Shape-Shift" . Berkeley Lab News Center . Retrieved 2023-09-10 .
^ "NP A Change in Structure for a S... | U.S. DOE Office of Science(SC)" . science.osti.gov . 2019-08-01. Retrieved 2023-09-10 .
^ Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*". Chinese Physics C . 45 (3): 030003. doi :10.1088/1674-1137/abddaf .
^ Jin, Y.; et al. (2021). "First observation of the four-proton unbound nucleus 18 Mg". Physical Review Letters . 127 (262502): 262502. doi :10.1103/PhysRevLett.127.262502 . OSTI 1837749 . PMID 35029460 . S2CID 245434485 .
^ Crawford, H. L.; Tripathi, V.; Allmond, J. M.; et al. (2022). "Crossing N = 28 toward the neutron drip line: first measurement of half-lives at FRIB" . Physical Review Letters . 129 (212501): 212501. Bibcode :2022PhRvL.129u2501C . doi :10.1103/PhysRevLett.129.212501 . PMID 36461950 . S2CID 253600995 .
Group
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Period
Hydrogen and alkali metals
Alkaline earth metals
Pnictogens
Chalcogens
Halogens
Noble gases
①
1
2
②
3
4
5
6
7
8
9
10
③
11
12
13
14
15
16
17
18
④
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
⑤
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
⑥
55
56
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
⑦
87
88
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
⑧
119
120
57
58
59
60
61
62
63
64
65
66
67
68
69
70
89
90
91
92
93
94
95
96
97
98
99
100
101
102