Isotopes of silicon

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.

List of isotopes

|-id=Silicon-22 | rowspan=3|²²Si | rowspan=3 style="text-align:right" | 14 | rowspan=3 style="text-align:right" | 8 | rowspan=3|22.034168(58) | rowspan=3|28.7(11)&nbsp;ms | β⁺, p (62%) | ²¹Mg | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β⁺ (37%) | ²²Al |- | β⁺, 2p (0.7%) | ²⁰Na |-id=Silicon-23 | rowspan=3|²³Si | rowspan=3 style="text-align:right" | 14 | rowspan=3 style="text-align:right" | 9 | rowspan=3|23.025083(17) | rowspan=3|42.3(4)&nbsp;ms | β⁺, p (88%) | ²²Mg | rowspan=3|3/2+# | rowspan=3| | rowspan=3| |- | β⁺ (8%) | ²³Al |- | β⁺, 2p (3.6%) | ²¹Na |-id=Silicon-24 | rowspan=2|²⁴Si | rowspan=2 style="text-align:right" | 14 | rowspan=2 style="text-align:right" | 10 | rowspan=2|24.011535(21) | rowspan=2|143.2&nbsp;(21)&nbsp;ms | β⁺ (65.5%) | ²⁴Al | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β⁺, p (34.5%) | ²³Mg |-id=Silicon-25 | rowspan=2|²⁵Si | rowspan=2 style="text-align:right" | 14 | rowspan=2 style="text-align:right" | 11 | rowspan=2|25.004109(11) | rowspan=2|220.6(10)&nbsp;ms | β⁺ (65%) | ²⁵Al | rowspan=2|5/2+ | rowspan=2| | rowspan=2| |- | β⁺, p (35%) | ²⁴Mg |-id=Silicon-26 | ²⁶Si | style="text-align:right" | 14 | style="text-align:right" | 12 | 25.99233382(12) | 2.2453(7)&nbsp;s | β⁺ | ²⁶Al | 0+ | | |-id=Silicon-27 | ²⁷Si | style="text-align:right" | 14 | style="text-align:right" | 13 | 26.98670469(12) | 4.117(14)&nbsp;s | β⁺ | ²⁷Al | 5/2+ | | |- | ²⁸Si | style="text-align:right" | 14 | style="text-align:right" | 14 | 27.97692653442(55) | colspan=3 align=center|Stable | 0+ | 0.92223(19) | 0.92205–0.92241 |- | ²⁹Si | style="text-align:right" | 14 | style="text-align:right" | 15 | 28.97649466434(60) | colspan=3 align=center|Stable | 1/2+ | 0.04685(8) | 0.04678–0.04692 |-id=Silicon-30 | ³⁰Si | style="text-align:right" | 14 | style="text-align:right" | 16 | 29.973770137(23) | colspan=3 align=center|Stable | 0+ | 0.03092(11) | 0.03082–0.03102 |-id=Silicon-31 | ³¹Si | style="text-align:right" | 14 | style="text-align:right" | 17 | 30.975363196(46) | 157.16(20)&nbsp;min | β^− | ³¹P | 3/2+ | | |-id=Silicon-32 | ³²Si | style="text-align:right" | 14 | style="text-align:right" | 18 | 31.97415154(32) | 157(7)&nbsp;y | β^− | ³²P | 0+ | trace | cosmogenic |-id=Silicon-33 | ³³Si | style="text-align:right" | 14 | style="text-align:right" | 19 | 32.97797696(75) | 6.18(18)&nbsp;s | β^− | ³³P | 3/2+ | | |- | ³⁴Si | style="text-align:right" | 14 | style="text-align:right" | 20 | 33.97853805(86) | 2.77(20)&nbsp;s | β^− | ³⁴P | 0+ | | |-id=Silicon-34m | style="text-indent:1em" |^34mSi | colspan=3 style="text-indent:2em" | 4256.1(4) keV | <210&nbsp;ns | IT | ³⁴Si | (3−) | | |-id=Silicon-35 | rowspan=2|³⁵Si | rowspan=2 style="text-align:right" | 14 | rowspan=2 style="text-align:right" | 21 | rowspan=2|34.984550(38) | rowspan=2|780(120)&nbsp;ms | β^− | ³⁵P | rowspan=2|7/2−# | rowspan=2| | rowspan=2| |- | β^−, n? | ³⁴P |-id=Silicon-36 | rowspan=2|³⁶Si | rowspan=2 style="text-align:right" | 14 | rowspan=2 style="text-align:right" | 22 | rowspan=2|35.986649(77) | rowspan=2|503(2)&nbsp;ms | β^− (88%) | ³⁶P | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β^−, n (12%) | ³⁵P |-id=Silicon-37 | rowspan=3|³⁷Si | rowspan=3 style="text-align:right" | 14 | rowspan=3 style="text-align:right" | 23 | rowspan=3|36.99295(12) | rowspan=3|141.0(35)&nbsp;ms | β^− (83%) | ³⁷P | rowspan=3|(5/2−) | rowspan=3| | rowspan=3| |- | β^−, n (17%) | ³⁶P |- | β^−, 2n? | ³⁵P |-id=Silicon-38 | rowspan=2|³⁸Si | rowspan=2 style="text-align:right" | 14 | rowspan=2 style="text-align:right" | 24 | rowspan=2|37.99552(11) | rowspan=2|63(8)&nbsp;ms | β^− (75%) | ³⁸P | rowspan=2|0+ | rowspan=2| | rowspan=2| |- | β^−, n (25%) | ³⁷P |-id=Silicon-39 | rowspan=3|³⁹Si | rowspan=3 style="text-align:right" | 14 | rowspan=3 style="text-align:right" | 25 | rowspan=3|39.00249(15) | rowspan=3|41.2(41)&nbsp;ms | β^− (67%) | ³⁹P | rowspan=3|(5/2−) | rowspan=3| | rowspan=3| |- | β^−, n (33%) | ³⁸P |- | β^−, 2n? | ³⁷P |-id=Silicon-40 | rowspan=3|⁴⁰Si | rowspan=3 style="text-align:right" | 14 | rowspan=3 style="text-align:right" | 26 | rowspan=3|40.00608(13) | rowspan=3|31.2(26)&nbsp;ms | β^− (62%) | ⁴⁰P | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β^−, n (38%) | ³⁹P |- | β^−, 2n? | ³⁸P |-id=Silicon-41 | rowspan=3|⁴¹Si | rowspan=3 style="text-align:right" | 14 | rowspan=3 style="text-align:right" | 27 | rowspan=3|41.01417(32)# | rowspan=3|20.0(25)&nbsp;ms | β^−, n (>55%) | ⁴⁰P | rowspan=3|7/2−# | rowspan=3| | rowspan=3| |- | β^− (<45%) | ⁴¹P |- | β^−, 2n? | ³⁹P |-id=Silicon-42 | rowspan=3|⁴²Si | rowspan=3 style="text-align:right" | 14 | rowspan=3 style="text-align:right" | 28 | rowspan=3|42.01808(32)# | rowspan=3|15.5(4&nbsp;(stat), 16&nbsp;(sys))&nbsp;ms | β^− (51%) | ⁴²P | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β^−, n (48%) | ⁴¹P |- | β^−, 2n (1%) | ⁴⁰P |-id=Silicon-43 | rowspan=3|⁴³Si | rowspan=3 style="text-align:right" | 14 | rowspan=3 style="text-align:right" | 29 | rowspan=3|43.02612(43)# | rowspan=3|13(4&nbsp;(stat), 2&nbsp;(sys))&nbsp;ms | β^−, n (52%) | ⁴²P | rowspan=3|3/2−# | rowspan=3| | rowspan=3| |- | β^− (27%) | ⁴³P |- | β^−, 2n (21%) | ⁴¹P |-id=Silicon-44 | rowspan=3|⁴⁴Si | rowspan=3 style="text-align:right" | 14 | rowspan=3 style="text-align:right" | 30 | rowspan=3|44.03147(54)# | rowspan=3|4#&nbsp;ms [>360&nbsp;ns] | β^−? | ⁴⁴P | rowspan=3|0+ | rowspan=3| | rowspan=3| |- | β^−, n? | ⁴³P |- | β^−, 2n? | ⁴²P |-id=Silicon-45 | ⁴⁵Si | style="text-align:right" | 14 | style="text-align:right" | 31 | 45.03982(64)# | 4#&nbsp;ms | | | 3/2−# | | |-id=Silicon-46 | ⁴⁶Si | style="text-align:right" | 14 | style="text-align:right" | 32 | | | | | | |

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. Extremely pure (>99.9998%) samples of ²⁸Si can be produced through selective ionization and deposition of ²⁸Si from silane gas. 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 sphere of the isotope and determining the exact number of atoms in the sample.

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.

Silicon-29

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

Silicon-34

Silicon-34 is a radioactive isotope with a half-life of 2.8&nbsp;seconds. In addition to the usual N&nbsp;=&nbsp;20 closed shell, the nucleus also shows a strong Z&nbsp;=&nbsp;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. Silicon-34 has an unusual "bubble" structure where the proton distribution is less dense at the center than near the surface, as the 2s_1/2 proton orbital is almost unoccupied in the ground state, unlike in ³⁶S where it is almost full. 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 .

See also

Daughter products other than silicon

• Isotopes of phosphorus
• Isotopes of aluminum
• Isotopes of magnesium
• Isotopes of sodium

References

External links

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