Isotopes of silicon

Main isotopes of Chemistry:silicon (14Si) | Iso­tope | Decay

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| abun­dance | half-life (t1/2) | mode | pro­duct
28Si  | 92.2%  | stable
29Si  | 4.7%  | stable
30Si  | 3.1%  | stable
31Si  | trace | 2.62 h  | β− | 31P
32Si  | trace  | 153 y  | β− | 32P
Standard atomic weight Ar, standard(Si)|

* [28.084, 28.086][1]
* Conventional: 28.085

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Silicon (14Si) has 25 known isotopes, with mass number ranging from 22 to 46. 28Si (the most abundant isotope, at 92.24%), 29Si (4.67%), and 30Si (3.07%) are stable. The longest-lived radioisotope is 32Si, which occurs naturally in tiny quantities from cosmic ray spallation of argon. Its half-life has been determined to be approximately 157 years; it beta decays with energy 0.21 MeV to 32P, which in turn beta-decays, with half-life 14.269 days to 32S; neither step has gamma emission. After 32Si, 31Si has the second longest half-life at 157.2 minutes. All others have half-lives under 7 seconds.

A chart showing the relative abundances of the naturally occurring isotopes of silicon.

## Contents

* 1 List of isotopes
* 2 Silicon-28
* 3 Silicon-29
* 4 Silicon-34
* 5 See also
* 6 References
* 7 External links

## List of isotopes

Nuclide
[n 1] | Z | N | Isotopic mass (u)
[n 2][n 3] | Half-life
[n 4] | Decay
mode
[n 5] | Daughter
isotope
[n 6] | Spin and
parity
[n 7][n 4] | Physics:Natural abundance (mole fraction)

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Excitation energy  | Normal proportion  | Range of variation
22Si  | 14  | 8  | 22.034168(58)[2] | 2007 | 28.7(11) ms  | β+, p (62%)  | 21Mg  | 0+  |  |
β+ (37%)  | 22Al
β+, 2p (0.7%)  | 20Na
23Si  | 14  | 9  | 23.025083(17)[2] | 1986 | 42.3(4) ms  | β+, p (88%)  | 22Mg  | 3/2+#  |  |
β+ (8%)  | 23Al
β+, 2p (3.6%)  | 21Na
24Si  | 14  | 10  | 24.011535(21)  | 1979 | 143.2 (21) ms  | β+ (65.5%)  | 24Al  | 0+  |  |
β+, p (34.5%)  | 23Mg
25Si  | 14  | 11  | 25.004109(11)  | 1963 | 220.6(10) ms  | β+ (65%)  | 25Al  | 5/2+  |  |
β+, p (35%)  | 24Mg
26Si  | 14  | 12  | 25.99233382(12)  | 1960 | 2.2453(7) s  | β+ | 26Al  | 0+  |  |
27Si  | 14  | 13  | 26.98670469(12)  | 1939 | 4.117(14) s  | β+ | 27Al | 5/2+  |  |
28Si  | 14  | 14  | 27.97692653442(55)  | 1920 | Stable | 0+  | 0.92223(19)  | 0.92205–0.92241
29Si  | 14  | 15  | 28.97649466434(60)  | 1920 | Stable | 1/2+  | 0.04685(8)  | 0.04678–0.04692
30Si  | 14  | 16  | 29.973770137(23)  | 1924 | Stable | 0+  | 0.03092(11)  | 0.03082–0.03102
31Si  | 14  | 17  | 30.975363196(46)  | 1934 | 157.16(20) min  | β− | 31P | 3/2+  | trace |
32Si  | 14  | 18  | 31.97415154(32)  | 1953 | 157(7) y  | β− | 32P  | 0+  | trace | cosmogenic
33Si  | 14  | 19  | 32.97797696(75)  | 1971 | 6.18(18) s  | β− | 33P  | 3/2+  |  |
34Si  | 14  | 20  | 33.97853805(86)  | 1971 | 2.77(20) s  | β− | 34P  | 0+  |  |
34mSi  | 4256.1(4) keV  | (1989)[n 8] | <210 ns  | IT  | 34Si  | (3−)  |  |
35Si  | 14  | 21  | 34.984550(38)  | 1971 | 780(120) ms  | β− | 35P  | 7/2−#  |  |
β−, n?  | 34P
36Si  | 14  | 22  | 35.986649(77)  | 1971 | 503(2) ms  | β− (88%)  | 36P  | 0+  |  |
β−, n (12%)  | 35P
37Si  | 14  | 23  | 36.99295(12)  | 1979 | 141.0(35) ms  | β− (83%)  | 37P  | (5/2−)  |  |
β−, n (17%)  | 36P
β−, 2n?  | 35P
38Si  | 14  | 24  | 37.99552(11)  | 1979 | 63(8) ms  | β− (75%)  | 38P  | 0+  |  |
β−, n (25%)  | 37P
39Si  | 14  | 25  | 39.00249(15)  | 1979 | 41.2(41) ms  | β− (67%)  | 39P  | (5/2−)  |  |
β−, n (33%)  | 38P
β−, 2n?  | 37P
40Si  | 14  | 26  | 40.00608(13)  | 1989 | 31.2(26) ms  | β− (62%)  | 40P  | 0+  |  |
β−, n (38%)  | 39P
β−, 2n?  | 38P
41Si  | 14  | 27  | 41.01417(32)#  | 1989 | 20.0(25) ms  | β−, n (>55%)  | 40P  | 7/2−#  |  |
β− (<45%)  | 41P
β−, 2n?  | 39P
42Si  | 14  | 28  | 42.01808(32)#  | 1990 | 15.5(4 (stat), 16 (sys)) ms[3] | β− (51%)  | 42P  | 0+  |  |
β−, n (48%)  | 41P
β−, 2n (1%)  | 40P
43Si  | 14  | 29  | 43.02612(43)#  | 2002 | 13(4 (stat), 2 (sys)) ms[3] | β−, n (52%)  | 42P  | 3/2−#  |  |
β− (27%)  | 43P
β−, 2n (21%)  | 41P
44Si  | 14  | 30  | 44.03147(54)#  | 2007 | 4# ms [>360 ns]  | β−?  | 44P  | 0+  |  |
β−, n?  | 43P
β−, 2n?  | 42P
45Si[4] | 14  | 31  | 45.03982(64)#  | 2024 | 4# ms  |  |  | 3/2−#  |  |
46Si[4] | 14  | 32  |  | 2024 |  |  |  |  |  |

1. ↑ mSi - Excited nuclear isomer.
2. ↑ ( ) - Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. ↑ # - Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. ↑ 4.0 4.1 # - Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
5. ↑ Modes of decay:  IT: | Isomeric transition

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n: | Neutron emission
p: | Proton emission
6. ↑ Bold symbol as daughter - Daughter product is stable.
7. ↑ ( ) spin value - Indicates spin with weak assignment arguments.
8. ↑ Half-life only inferred and not measured.

## Silicon-28

Silicon-28, the most abundant isotope of silicon, is of particular interest in the construction of quantum computers when highly enriched, as the presence of 29Si in a sample of silicon contributes to quantum decoherence.[5] Extremely pure (>99.9998%) samples of 28Si can be produced through selective ionization and deposition of 28Si from silane gas.[6] Due to the extremely high purity that can be obtained in this manner, the Avogadro project sought to develop a new definition of the kilogram by making a 93.75 mm (3.691 in) sphere of the isotope and determining the exact number of atoms in the sample.[7][8]

Silicon-28 is produced in stars during the alpha process and the oxygen-burning process, and drives the silicon-burning process in massive stars shortly before they go supernova.[9][10]

## Silicon-29

Silicon-29 is of note as the only stable silicon isotope with a nonzero nuclear spin (I = 1/2).[11] As such, it can be employed in nuclear magnetic resonance and hyperfine transition studies, for example to study the properties of the so-called A-center defect in pure silicon.[12]

## Silicon-34

Silicon-34 is a radioactive isotope with a half-life of 2.8 seconds.[13] In addition to the usual N = 20 closed shell, the nucleus also shows a strong Z = 14 shell closure, making it behave like a doubly magic spherical nucleus, except that it is also located two protons above an island of inversion.[14] Silicon-34 has an unusual "bubble" structure where the proton distribution is less dense at the center than near the surface, as the 2s1/2 proton orbital is almost unoccupied in the ground state, unlike in 36S where it is almost full.[15][16] Silicon-34 is one of the known cluster decay emission particles; it is produced in the decay of 242Cm with a branching ratio of approximately 1×10−16.[17]

## See also

Daughter products other than silicon

* Isotopes of phosphorus
* Isotopes of aluminum
* Isotopes of magnesium
* Isotopes of sodium

## References

1. ↑ Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna 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.
2. ↑ 2.0 2.1 Xing, Y. M.; Luo, Y. F.; Zhang, Y. H.; Wang, M.; Zhou, X. H.; Li, J. G.; Li, K. H.; Yuan, Q. et al. (2 July 2025). "Z = 14 Magicity Revealed by the Mass of the Proton Dripline Nucleus Si 22". Physical Review Letters 135 (1). doi:10.1103/ffwt-n7yc. PMID 40743097.
3. ↑ 3.0 3.1 Crawford, H. L.Expression error: Unrecognized word "et". (2022). "Crossing N = 28 toward the neutron drip line: first measurement of half-lives at FRIB". Physical Review Letters 129 (212501). doi:10.1103/PhysRevLett.129.212501. PMID 36461950. Bibcode: 2022PhRvL.129u2501C.
4. ↑ 4.0 4.1 Yoshimoto, Masahiro; Suzuki, Hiroshi; Fukuda, Naoki; Takeda, Hiroyuki; Shimizu, Yohei; Yanagisawa, Yoshiyuki; Sato, Hiromi; Kusaka, Kensuke et al. (2024). "Discovery of Neutron-Rich Silicon Isotopes 45,46Si". Progress of Theoretical and Experimental Physics (Oxford University Press (OUP)) 2024 (10). doi:10.1093/ptep/ptae155. ISSN 2050-3911.
5. ↑ "Beyond Six Nines: Ultra-enriched Silicon Paves the Road to Quantum Computing" (in en). NIST. 2014-08-11. https://www.nist.gov/news-events/news/2014/08/beyond-six-nines-ultra-enriched-silicon-paves-road-quantum-computing.
6. ↑ Dwyer, K J; Pomeroy, J M; Simons, D S; Steffens, K L; Lau, J W (2014-08-30). "Enriching 28 Si beyond 99.9998 % for semiconductor quantum computing". Journal of Physics D: Applied Physics 47 (34). doi:10.1088/0022-3727/47/34/345105. ISSN 0022-3727. https://iopscience.iop.org/article/10.1088/0022-3727/47/34/345105.
7. ↑ Powell, Devin (1 July 2008). "Roundest Objects in the World Created". New Scientist. Retrieved 16 June 2015.
8. ↑ Keats, Jonathon. "The Search for a More Perfect Kilogram". Wired 19 (10). https://www.wired.com/2011/09/ff-kilogram/. Retrieved 16 December 2023.
9. ↑ Woosley, S.; Janka, T. (2006). "The physics of core collapse supernovae". Nature Physics 1 (3): 147–154. doi:10.1038/nphys172. Bibcode: 2005NatPh...1..147W.
10. ↑ Narlikar, Jayant V. (1995). From Black Clouds to Black Holes. World Scientific. p. 94. ISBN 978-981-02-2033-4. https://books.google.com/books?id=0_gmjz-L70EC&pg=PA94.
11. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
12. ↑ Watkins, G. D.; Corbett, J. W. (1961-02-15). "Defects in Irradiated Silicon. I. Electron Spin Resonance of the Si- A Center" (in en). Physical Review 121 (4): 1001–1014. doi:10.1103/PhysRev.121.1001. ISSN 0031-899X. Bibcode: 1961PhRv..121.1001W. https://link.aps.org/doi/10.1103/PhysRev.121.1001.
13. ↑ Cite error: Invalid `<ref>` tag; no text was provided for refs named `NUBASE2020`
14. ↑ Lică, R.; Rotaru, F.; Borge, M. J. G.; Grévy, S.; Negoiţă, F.; Poves, A.; Sorlin, O.; Andreyev, A. N. et al. (11 September 2019). "Normal and intruder configurations in Si 34 populated in the β − decay of Mg 34 and Al 34". Physical Review C 100 (3). doi:10.1103/PhysRevC.100.034306.
15. ↑ "Physicists find atomic nucleus with a 'bubble' in the middle". 24 October 2016. https://www.sciencenews.org/article/physicists-find-atomic-nucleus-bubble-middle.
16. ↑ Mutschler, A.; Lemasson, A.; Sorlin, O.; Bazin, D.; Borcea, C.; Borcea, R.; Dombrádi, Z.; Ebran, J.-P. et al. (February 2017). "A proton density bubble in the doubly magic 34Si nucleus". Nature Physics 13 (2): 152–156. doi:10.1038/nphys3916.
17. ↑ Bonetti, R.; Guglielmetti, A. (2007). "Cluster radioactivity: an overview after twenty years". Romanian Reports in Physics 59: 301–310. http://www.rrp.infim.ro/2007_59_2/10_bonetti.pdf.

## External links

* Silicon isotopes data from The Berkeley Laboratory Isotopes Project's

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Isotopes of the chemical elements

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* Table of nuclides
* Categories: Isotopes
* Tables of nuclides
* Metastable isotopes
* Isotopes by element

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