Isotopes Of Silicon

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

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)
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
    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

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. 



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