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Isotopes of Silicon

List, data and properties of all known isotopes of Silicon.

Content
Atomic properties
Decay properties
NMR active nuclides
Radiation protection
References
Silicon isotopes

Of the 23 known isotopes of silicon, only the isotopes 28Si, 29Si and 30Si are stable and found in nature; all others are radioisotopes. 32Si is formed in the atmosphere by the action of cosmic rays on argon atoms and decays to phosphorus-31 with a half-life of 153 years.

 

Naturally Occurring Silicon Isotopes

Atomic Mass maQuantityHalf-lifeSpin
Silicon
Isotopic mixture		28,085 u100 %
Isotope 28Si27,976926535(3) u92,254 %stable0+
Isotope 29Si28,976494665(3) u4,673 %stable1/2+
Isotope 30Si29,97377001(2) u3,073 %stable0+

 

The natural isotopic abundances (isotopic ratio) of naturally occurring silicon can vary to a greater or lesser extent, so that the atomic mass fluctuates between 28.084 and 28.086.

< p>All other silicon radionuclides have half-lives in the range of seconds or much less.

The particularly stable silicon-28 core is created in stellar fusion processes during oxygen burning.

 

Isotope Table: Silicon

The two following tables list the most important data and properties of the Silicon isotopes. Further information on the individual Silicon isotopes is listed on separate pages and can be accessed via the link in column 1.

 

Atomic Properties

Isotope
Nuclide		ENAtomic Mass
[Nuclear Mass]
{Mass Excess}		Spin I
(h/2π)		Parent
123456
Silicon-222214Si822.03579(54) u
[22.02811 u]
{33.33817 MeV}		0+
Silicon-232314Si923.02544(54) u
[23.01776 u]
{23.69721 MeV}		(5/2)+
Silicon-242414Si1024.011535(21) u
[24.003855 u]
{10.74478 MeV}		0+
Silicon-252514Si1125.004108046(10735) u
[24.996428 u]
{3.82662 MeV}		5/2+
Silicon-262614Si1225.9923338(12) u
[25.9846538 u]
{-7.14102 MeV}		0+26P
Silicon-272714Si1326.98670469(12) u
[26.9790247 u]
{-12.3845 MeV}		5/2+27P
28S
Silicon-282814Si1427.976926535(3) u
[27.9692465 u]
{-21.49279 MeV}		0+28P
28Al
29S
31Ar
32Cl
Silicon-292914Si1528.976494665(3) u
[28.9688146 u]
{-21.89508 MeV}		1/2+29P
29Al
Silicon-303014Si1629.97377001(2) u
[29.96609 u]
{-24.43308 MeV}		0+30P
30Al
Silicon-313114Si1730.97536319(5) u
[30.9676832 u]
{-22.94904 MeV}		3/2+31Al
Silicon-323214Si1831.9741515(3) u
[31.9664715 u]
{-24.07772 MeV}		0+32Al
Silicon-333314Si1932.9779770(8) u
[32.970297 u]
{-20.51429 MeV}		3/2+33Al
34Al
Silicon-343414Si2033.978575(15) u
[33.970895 u]
{-19.95726 MeV}		0+34Al
35Al
Silicon-353514Si2134.98455(4) u
[34.97687 u]
{-14.39158 MeV}		(7/2)-35Al
Silicon-363614Si2235.98665(8) u
[35.97897 u]
{-12.43544 MeV}		0+
Silicon-373714Si2336.99295(12) u
[36.98527 u]
{-6.56703 MeV}		(5/2-)
Silicon-383814Si2437.99552(11) u
[37.98784 u]
{-4.17309 MeV}		0+
Silicon-393914Si2539.00249(15) u
[38.99481 u]
{2.31942 MeV}		(5/2-)
Silicon-404014Si2640.00583(37) u
[39.99815 u]
{5.43061 MeV}		0+
Silicon-414114Si2741.01301(60) u
[41.00533 u]
{12.11874 MeV}		7/2-
Silicon-424214Si2842.01808(32) u
[42.0104 u]
{16.84141 MeV}		0+
Silicon-434314Si2943.02480(64) u
[43.01712 u]
{23.10105 MeV}		3/2-
Silicon-444414Si3044.03061(64) u
[44.02293 u]
{28.51303 MeV}		0+

 

Radioactive Decay Properties

IsotopeRadioactive DecayExtern
Half-lifeDecay ModeProbabilityEnergy
789101112
Si-2229(2) msEC/β+ → 22Al
β+, p → 21Mg		68(4) %
32(4) %		15.14(64) MeV
AL
Si-2342.3(4) msEC/β+ → 23Al
ε, p → 22Mg
ε, 2p → 21Na		25.4 %
71 %
3.6 %		17.002 MeV
16.880 MeV
11.378 MeV		AL
Si-24140(8) msEC/β+ → 24Al
β+, p → 23Mg		62(4) %
38(4) %		10.794(19) MeV
8.939 MeV		AL
Si-25220(3) msEC/β+ → 25Al
β+, p → 24Mg		65(2) %
35(2) %		12.743(10) MeV
10.469 MeV		AL
Si-262.2453(7) sEC/β+ → 26Al100 %5.06914(13) MeVAL
Si-274.15(4) sEC/β+ → 27Al100 %4.81236 MeVAL
Si-28stableAL
Si-29stableAL
Si-30stableAL
Si-31157.36(26) minβ- → 31P100 %1.49150(4) MeVAL
Si-32153(19) aβ- → 32P100 %0.2272(3) MeVAL
Si-336.11(21) sβ- → 33P100 %5.8230(13) MeVAL
Si-342.77(20) sβ- → 34P100 %4.592(14) MeVAL
Si-350.78(12) sβ- → 35P
β-, n → 34P		> 95 %
< 5 %		10.4974 MeV
2.11698 MeV		AL
Si-360.45(6) sβ- → 36P
β-, n → 35P		> 90 %
< 10 %		7.83339 MeV
4.3688 MeV		AL
Si-3790(60) msβ- → 37P
β-, n → 36P
β-, 2n → 35P		83(13) %
17(13) %
?		12.4016 MeV
5.5854 MeV
AL
Si-3863(8) msβ- → 38P
β-, n → 37P		75(10) %
25(10) %		10.45(13) MeV
6.75(11) MeV		AL
Si-3947.5(20) msβ- → 39P
β-, n → 38P
β-, 2n → 37P		100 %
?
?		15.09(18) MeV
8.87(15) MeV
AL
Si-4033.0(10) msβ- → 40P
β-, n → 39P
β-, 2n → 38P		100 %
?
?		13.54(38) MeV
10.13(36) MeV
AL
Si-4120.0(25) msβ- → 41P
β-, n → 40P		100 %
> 0 %		17.10(57) MeV
12.16(58) MeV		AL
Si-4212.5(35) msβ- → 42P
β-, n → 41P
β-, 2n → 40P		100 %
?
?		15.75(32) MeV
13.748(323) MeV
AL
Si-4360 nsβ- → 43P
β-, n → 42P
β-, 2n → 41P		?
?
?		18.42(81) MeV
14.02(67) MeV
AL
Si-44360 nsβ- → 44P
β-, n → 43P		100 %
?		18.06(78) MeV
15.76(81) MeV		AL

 

Notes (related to the columns):

1 - name of the nuclide, isotope.
2 - E: isotope symbol with mass number (superscript; number of nucleons) and Atomic number (subscript; number of protons).
3 - N: number of neutrons.
4 - relative atomic mass of the Silicon isotope (isotopic mass including electrons) and the mass of the atomic nucleus in square brackets (nuclear mass, nuclide mass without electrons), each related to 12C = 12.00000 [2]. In addition, the mass excess is given in MeV.
5 - nuclear spin I, unit: h/2π.
6 - source nuclides: Possible, assumed or actual source nuclides (mother nuclides, parent nuclides). If applicable, the corresponding decay modes can be found in the data for the respective starting nuclide.

7 - isotope notation in short form.
8 - decay: half-live of the Silicon isotope (a = years; ; d = days; h = hours; min = minutes; s = seconds).
9 - decay mode: type of decay into the respective daughter nuclides with n = neutron emission; p = proton emission; α = alpha decay; β- = beta minus decay with electron emission; EC = electron capture; β+ = positron emission; ε = β+ and/or EC; Iso = isomeric transition; CD = cluster decay; SF = spontaneous decay.
10 - decay probability in percent (%).
11 - decay energy; Particle energy related to decay type.
12 - other information and notes: AL = Adopted Levels (link to external data [1]).

Miscellaneous:

()- Numbers in brackets: uncertainty to represent the spread of the reported value.
~ - Theoretical values or systematic trends.
  - unlisted-: Nuclides that have already been mentioned in the literature but for some reason can no longer be found in the current nuclide tables because their discovery e.g. has not confirmed.

 

NMR active Silicon nuclides

Nuclide
quantity 1)
spin		Nuclear
magnetic
moment
μ/μN		Gyromagnetic ratio
{Quadrupole moment}		Resonant
frequency
v0 bei 1 T		Relative
sensitivity
H0 = const.
v0 = const. 3)
29Si
4,673 %
1/2+		-0,555052(3)- 5,3188
{}		8,46550,00786
0,1988

1) Quantity Percentage of natural occurrence.

2) Gyromagnetic ratio: 107 rad T-1 s-1
    Quadrupole moment: Q [barn] = [100 fm2]

3) Related to 1H = 1,000.

 

Radiation Protection

According to the Radiation Protection Ordinance (StrlSchV 2018, Germany), the following values (columns 1 to 7) apply to the handling of Silicon radionuclides:

NuclideLimit ValueHASS limitSCDaughter NuclidesHalf-life
Si-31106 Bq1000 Bq/g10 TBq100 Bq/cm22.6 h
Si-32+106 Bq100 Bq/g7 Bq132.0 a (s.o.)

(HASS = High-Activity Sealed Radioactive Sources; SC = surface contamination)

 

Literature Sources and References

Properties of the Silicon nucleides

[1] - NuDat: National Nuclear Data Center, Brookhaven National Laboratory, based on ENSDF and the Nuclear Wallet Cards.

[2] - G. Audi et. al.: The NUBASE evaluation of nuclear and decay properties. Nuclear Physics, (2003), DOI 10.1016/j.nuclphysa.2003.11.001.

[3] - Live Chart of Nuclides. Nuclear structure and decay data.

Silicon: NMR properties - 29Si-NMR

[4] - N. J. Stone: Table of nuclear magnetic dipole and electric quadrupole moments. Atomic Data and Nuclear Data Tables, (2005), DOI 10.1016/j.adt.2005.04.001.

[5] - Pekka Pyykkö: Year-2008 nuclear quadrupole moments. Molecular Physics, (2008), DOI 10.1080/00268970802018367.

[6] - Pekka Pyykkö: Year-2017 nuclear quadrupole moments. Molecular Physics, (2018), DOI 10.1080/00268976.2018.1426131.

[7] - N. J. Stone: Table of recommended nuclear magnetic dipole moments. IAEA, (2019).

More sources:

[8] - Isotopic abundances, atomic weights and isotopic masses: see respective keyword.

 

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