Isotopes of silicon
Silicon (14Si) has 23 known isotopes, with mass numbers ranging from 22 to 44. 28Si (the most abundant isotope, at 92.23%), 29Si (4.67%), and 30Si (3.1%) are stable. The longest-lived radioisotope is 32Si, which is produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately 150 years (with decay energy 0.21 MeV), and it decays by beta emission to 32P (which has a 14.28-day half-life)[2] and then to 32S. After 32Si, 31Si has the second longest half-life at 157.3 minutes. All others have half-lives under 7 seconds.
![](../I/m/Isotopes_of_Silicon.png)
A chart showing the relative abundances of the naturally occurring isotopes of silicon.
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Standard atomic weight Ar, standard(Si) |
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List of isotopes
Nuclide[3] [n 1] |
Z | N | Isotopic mass (Da)[4] [n 2][n 3] |
Half-life [n 4] |
Decay mode [n 5] |
Daughter isotope [n 6] |
Spin and parity [n 7][n 4] |
Natural abundance (mole fraction) | |
---|---|---|---|---|---|---|---|---|---|
Excitation energy | Normal proportion | Range of variation | |||||||
22Si | 14 | 8 | 22.03579(54)# | 29(2) ms | β+ (67.6%) | 22Al | 0+ | ||
β+, p (32.4%) | 21Mg | ||||||||
23Si | 14 | 9 | 23.02544(54)# | 42.3(4) ms | β+ (12%) | 23Al | 3/2+# | ||
β+, p (88%) | 21Mg | ||||||||
24Si | 14 | 10 | 24.011535(21) | 140(8) ms | β+ (62.4%) | 24Al | 0+ | ||
β+, p (37.6%) | 23Mg | ||||||||
25Si | 14 | 11 | 25.004109(11) | 220(3) ms | β+ (64.8%) | 25Al | 5/2+ | ||
β+, p (35.2%) | 24Mg | ||||||||
26Si | 14 | 12 | 25.9923338(12) | 2.2453(7) s | β+ | 26Al | 0+ | ||
27Si | 14 | 13 | 26.98670469(12) | 4.15(4) s | β+ | 27Al | 5/2+ | ||
28Si | 14 | 14 | 27.9769265350(5) | Stable | 0+ | 0.92223(19) | 0.92205–0.92241 | ||
29Si | 14 | 15 | 28.9764946653(6) | Stable | 1/2+ | 0.04685(8) | 0.04678–0.04692 | ||
30Si | 14 | 16 | 29.973770137(23) | Stable | 0+ | 0.03092(11) | 0.03082–0.03102 | ||
31Si | 14 | 17 | 30.97536319(5) | 157.36(26) min | β− | 31P | 3/2+ | ||
32Si | 14 | 18 | 31.9741515(3) | 153(19) y | β− | 32P | 0+ | trace | cosmogenic |
33Si | 14 | 19 | 32.9779770(8) | 6.18(18) s | β− | 33P | (3/2+) | ||
34Si | 14 | 20 | 33.978575(15) | 2.77(20) s | β− | 34P | 0+ | ||
34mSi | 4256.1(4) keV | <210 ns | IT | 34Si | (3−) | ||||
35Si | 14 | 21 | 34.98455(4) | 780(120) ms | β− (94.74%) | 35P | 7/2−# | ||
36Si | 14 | 22 | 35.98665(8) | 450(60) ms | β− (87.5%) | 36P | 0+ | ||
β−, n (12.5%) | 35P | ||||||||
37Si | 14 | 23 | 36.99295(12) | 90(60) ms | β− (83%) | 37P | (7/2−)# | ||
β−, n (17%) | 36P | ||||||||
38Si | 14 | 24 | 37.99552(11) | 90# ms [>1 μs] | β−, n | 37P | 0+ | ||
β− | 38P | ||||||||
39Si | 14 | 25 | 39.00249(15) | 47.5(20) ms | β− | 39P | 7/2−# | ||
40Si | 14 | 26 | 40.00583(37) | 33.0(10) ms | β− | 40P | 0+ | ||
41Si | 14 | 27 | 41.01301(60) | 20.0(25) ms | β− | 41P | 7/2−# | ||
42Si | 14 | 28 | 42.01768(54)# | 12.5(35) ms | β− | 42P | 0+ | ||
43Si | 14 | 29 | 43.02480(64)# | 15# ms [>260 ns] | 3/2−# | ||||
44Si | 14 | 30 | 44.03061(64)# | 10# ms | 0+ |
- mSi – Excited nuclear isomer.
- ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
- # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
- # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
-
Modes of decay:
IT: Isomeric transition n: Neutron emission p: Proton emission - Bold symbol as daughter – Daughter product is stable.
- ( ) spin value – Indicates spin with weak assignment arguments.
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References
- Meija, Juris; 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.
- Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
- Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001. - Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017). "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF). Chinese Physics C. 41 (3): 030003-1–030003-442. doi:10.1088/1674-1137/41/3/030003.
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