Isotopes of silicon (14Si)
Main isotopes[1] 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°(Si)
  • [28.084, 28.086]
  • 28.085±0.001 (abridged)[2][3]

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 14.27-day half-life)[1] 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.

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

List of isotopes

Nuclide
[n 1]		 Z N Isotopic mass (Da)[4]
[n 2][n 3]		 Half-life[1]
[n 4]		 Decay
mode[1]
[n 5]		 Daughter
isotope
[n 6]		 Spin and
parity[1]
[n 7][n 4]		 Natural abundance (mole fraction)
Excitation energy Normal proportion[1] Range of variation
22Si 14 8 22.03611(54)# 28.7(11) ms β+, p (62%) 21Mg 0+
β+ (37%) 22Al
β+, 2p (0.7%) 20Na
23Si 14 9 23.02571(54)# 42.3(4) ms β+, p (88%) 22Mg 3/2+#
β+ (8%) 23Al
β+, 2p (3.6%) 21Na
24Si 14 10 24.011535(21) 143.2 (21) ms β+ (65.5%) 24Al 0+
β+, p (34.5%) 23Mg
25Si 14 11 25.004109(11) 220.6(10) ms β+ (65%) 25Al 5/2+
β+, p (35%) 24Mg
26Si 14 12 25.99233382(12) 2.2453(7) s β+ 26Al 0+
27Si 14 13 26.98670469(12) 4.117(14) s β+ 27Al 5/2+
28Si 14 14 27.97692653442(55) Stable 0+ 0.92223(19) 0.92205–0.92241
29Si 14 15 28.97649466434(60) 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 30.975363196(46) 157.16(20) min β− 31P 3/2+
32Si 14 18 31.97415154(32) 157(7) y β− 32P 0+ trace cosmogenic
33Si 14 19 32.97797696(75) 6.18(18) s β− 33P 3/2+
34Si 14 20 33.97853805(86) 2.77(20) s β− 34P 0+
34mSi 4256.1(4) keV <210 ns IT 34Si (3−)
35Si 14 21 34.984550(38) 780(120) ms β− 35P 7/2−#
β−, n? 34P
36Si 14 22 35.986649(77) 503(2) ms β− (88%) 36P 0+
β−, n (12%) 35P
37Si 14 23 36.99295(12) 141.0(35) ms β− (83%) 37P (5/2−)
β−, n (17%) 36P
β−, 2n? 35P
38Si 14 24 37.99552(11) 63(8) ms β− (75%) 38P 0+
β−, n (25%) 37P
39Si 14 25 39.00249(15) 41.2(41) ms β− (67%) 39P (5/2−)
β−, n (33%) 38P
β−, 2n? 37P
40Si 14 26 40.00608(13) 31.2(26) ms β− (62%) 40P 0+
β−, n (38%) 39P
β−, 2n? 38P
41Si 14 27 41.01417(32)# 20.0(25) ms β−, n (>55%) 40P 7/2−#
β− (<45%) 41P
β−, 2n? 39P
42Si 14 28 42.01808(32)# 15.5(4 (stat), 16 (sys)) ms[5] β− (51%) 42P 0+
β−, n (48%) 41P
β−, 2n (1%) 40P
43Si 14 29 43.02612(43)# 13(4 (stat), 2 (sys)) ms[5] β−, n (52%) 42P 3/2−#
β− (27%) 43P
β−, 2n (21%) 41P
44Si 14 30 44.03147(54)# 4# ms [>360 ns] β−? 44P 0+
β−, n? 43P
β−, 2n? 42P
This table header & footer:
  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. 1 2 # – 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.

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.[6] Extremely pure (>99.9998%) samples of 28Si can be produced through selective ionization and deposition of 28Si from silane gas.[7] 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 determing the exact number of atoms in the sample.[8][9]

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.[10][11]

Silicon-29

Silicon-29 is of note as the only stable silicon isotope with a nuclear spin (I = 1/2).[12] 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.[13]

Silicon-34

Silicon-34 is a radioactive isotope wth a half-life of 2.8 seconds.[1] 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]

References

  1. 1 2 3 4 5 6 7 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.
  2. ↑ "Standard Atomic Weights: Silicon". CIAAW. 2009.
  3. ↑ Prohaska, Thomas; Irrgeher, Johanna; Benefield, Jacqueline; et al. (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.
  4. ↑ 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.
  5. 1 2 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.
  6. ↑ "Beyond Six Nines: Ultra-enriched Silicon Paves the Road to Quantum Computing". NIST. 2014-08-11.
  7. ↑ 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): 345105. doi:10.1088/0022-3727/47/34/345105. ISSN 0022-3727.
  8. ↑ Powell, Devin (1 July 2008). "Roundest Objects in the World Created". New Scientist. Retrieved 16 June 2015.
  9. ↑ Keats, Jonathon. "The Search for a More Perfect Kilogram". Wired. Retrieved 16 December 2023.
  10. ↑ Woosley, S.; Janka, T. (2006). "The physics of core collapse supernovae". Nature Physics. 1 (3): 147–154. arXiv:astro-ph/0601261. Bibcode:2005NatPh...1..147W. CiteSeerX 10.1.1.336.2176. doi:10.1038/nphys172. S2CID 118974639.
  11. ↑ Narlikar, Jayant V. (1995). From Black Clouds to Black Holes. World Scientific. p. 94. ISBN 978-9810220334.
  12. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
  13. ↑ Watkins, G. D.; Corbett, J. W. (1961-02-15). "Defects in Irradiated Silicon. I. Electron Spin Resonance of the Si- A Center". Physical Review. 121 (4): 1001–1014. doi:10.1103/PhysRev.121.1001. ISSN 0031-899X.
  14. ↑ Lică, R.; Rotaru, F.; Borge, M. J. G.; Grévy, S.; Negoiţă, F.; Poves, A.; Sorlin, O.; Andreyev, A. N.; Borcea, R.; Costache, C.; De Witte, H.; Fraile, L. M.; Greenlees, P. T.; Huyse, M.; Ionescu, A.; Kisyov, S.; Konki, J.; Lazarus, I.; Madurga, M.; Mărginean, N.; Mărginean, R.; Mihai, C.; Mihai, R. E.; Negret, A.; Nowacki, F.; Page, R. D.; Pakarinen, J.; Pucknell, V.; Rahkila, P.; Rapisarda, E.; Şerban, A.; Sotty, C. O.; Stan, L.; Stănoiu, M.; Tengblad, O.; Turturică, A.; Van Duppen, P.; Warr, N.; Dessagne, Ph.; Stora, T.; Borcea, C.; Călinescu, S.; Daugas, J. M.; Filipescu, D.; Kuti, I.; Franchoo, S.; Gheorghe, I.; Morfouace, P.; Morel, P.; Mrazek, J.; Pietreanu, D.; Sohler, D.; Stefan, I.; Şuvăilă, R.; Toma, S.; Ur, C. A. (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). arXiv:1908.11626. doi:10.1103/PhysRevC.100.034306.
  15. ↑ "Physicists find atomic nucleus with a 'bubble' in the middle". 24 October 2016. Retrieved 26 December 2023.
  16. ↑ Mutschler, A.; Lemasson, A.; Sorlin, O.; Bazin, D.; Borcea, C.; Borcea, R.; Dombrádi, Z.; Ebran, J.-P.; Gade, A.; Iwasaki, H.; Khan, E.; Lepailleur, A.; Recchia, F.; Roger, T.; Rotaru, F.; Sohler, D.; Stanoiu, M.; Stroberg, S. R.; Tostevin, J. A.; Vandebrouck, M.; Weisshaar, D.; Wimmer, K. (February 2017). "A proton density bubble in the doubly magic 34Si nucleus". Nature Physics. 13 (2): 152–156. arXiv:1707.03583. doi:10.1038/nphys3916.
  17. ↑ Bonetti, R.; Guglielmetti, A. (2007). "Cluster radioactivity: an overview after twenty years" (PDF). Romanian Reports in Physics. 59: 301–310. Archived from the original (PDF) on 19 September 2016.
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