镁共有22个已知同位素，质量数介于19-40之间，其中有3个是稳定的，其他都具有放射性。天然存在的镁同位素有3个，分别是24Mg、25Mg、26Mg，皆为稳定同位素。其他放射性同位素都不出现在自然界中，只有在实验室制造出来过，且半衰期都很短，非常不稳定，其中最长寿的是28Mg，半衰期为20.915小时。
Quick Facts 同位素, 衰变 ...
主要的镁同位素|
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| 标准原子质量 (Ar, 标准) | - [24.304, 24.307][1]
- 传统: 24.305
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More information 符号, Z ...
| 符号
|
Z
|
N
|
同位素质量（u）
[n 1][n 2]
|
半衰期
[n 1][n 2]
|
衰变
方式[2]
|
衰变
产物
[n 3]
|
原子核
自旋[n 1]
|
相对丰度
（莫耳分率）[3][n 2]
|
相对丰度
的变化量
（莫耳分率）[4]
|
| 18Mg[5]
|
12
|
6
|
|
|
2p
|
16Ne
|
0+
|
|
|
| 19Mg
|
12
|
7
|
19.03417(5)
|
5(3) ps
|
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+
|
|
|
24
Mg
|
12
|
12
|
23.985041700(14)
|
稳定
|
0+
|
0.78965(49)
|
[0.7888, 0.7905]
|
| 25Mg
|
12
|
13
|
24.98583692(3)
|
稳定
|
5/2+
|
0.10011(13)
|
[0.09988, 0.10034]
|
| 26Mg[n 4]
|
12
|
14
|
25.982592929(30)
|
稳定
|
0+
|
0.11025(38)
|
[0.1096, 0.1109]
|
| 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+
|
|
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Close
画上#号的数据代表没有经过实验的证明，仅为理论推测。
- Isotope masses from Ame2003 Atomic Mass Evaluation by G. Audi, A.H. Wapstra, C. Thibault, J. Blachot and O. Bersillon in Nuclear Physics A729 (2003).
- Half-life, spin, and isomer data selected from these sources. Editing notes on this article's talk page.
- Audi, Bersillon, Blachot, Wapstra. The Nubase2003 evaluation of nuclear and decay properties （页面存档备份，存于互联网档案馆）, Nuc. Phys. A 729, pp. 3-128 (2003).
- National Nuclear Data Center, Brookhaven National Laboratory. Information extracted from the NuDat 2.1 database （页面存档备份，存于互联网档案馆） (retrieved Sept. 2005).
- David R. Lide (ed.), Norman E. Holden in CRC Handbook of Chemistry and Physics, 85th Edition, online version. CRC Press. Boca Raton, Florida (2005). Section 11, Table of the Isotopes.
