Silicon-29
Properties and data of the isotope 29Si.
Silicon-29 is a naturally occurring, stable isotope of the chemical element silicon, which has 15 neutrons in its atomic nucleus in addition to the element-specific 14 protons; the sum of the number of these atomic nucleus building blocks results in a mass number of 29.
Silicon-29 was first identified as a distinct isotope in 1920 by measuring its mass spectrum [1].
See also: List of individual Silicon isotopes (and general data sources).
General data
Name of the isotope:Silicon-29; Si-29Symbol:29Si or 2914SiMass number A:29 (= number of nucleons)Atomic number Z:14 (= number of protons)Neutrons N:15Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.0714285714286 (= neutron-proton ratio)Neutron excess (N-Z):1Isotopic mass:28.9764946643(6) u (atomic weight of Silicon-29)Nuclide mass:28.9688146 u (calculated nuclear mass without electrons)Mass excess:-21.89508 MeVMass defect:0.2630295237 u (per nucleus)Nuclear binding energy:245.01042315 MeV (per nucleus)
8.44863528 MeV (average binding energy per nucleon)Separation energy:SN = 8.4736016(9) MeV (first neutron)
SP = 12.33333(5) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)1/2+Magnetic dipole moment:μ(μN) = -0.555052(3)Charge radius:3.1176(52) femtometer fmMirror nucleus:Phosphorus-29Year of discovery:1920
Parent Nuclides
Direct parent isotopes are: 29P, 29Al.
Occurrence
Comparison of the natural Silicon isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):
| | Atomic Mass ma | Quantity | Half-life | Spin |
|---|
Silicon
Isotopic mixture | 28.085 u | 100 % | | |
| Isotope 28Si | 27.9769265344(6) u | 92.254 %
[92.191 - 92.318 %] | stable | 0+ |
| Isotope 29Si | 28.9764946643(6) u | 4.673 %
[4.645 - 4.699 %] | stable | 1/2+ |
| Isotope 30Si | 29.973770137(23) u | 3.073 %
[3.037 - 3.110 %] | stable | 0+ |
NMR data
Nuclear magnetic properties and parameters of the NMR active Nuclide 29Si
Isotope:29Si-NMRQuantity:4.673 % [4.645 - 4.699 %]Spin:1/2+Nuclearmagnetic moment
μ/μN:-0.555052(3)Gyromagnetic ratio γ:0 · 107 rad T-1 s-1
0.00000 MHz T-1Nuclear g-factor:gl = -1.110104Resonance frequency:v0 = 8.4655 MHz at 1 TRelative Sensitivity:[related to 1H = 1.000]:
0.00786 (H0 = const.)
0.1988 (v0 = const.)
0.000368 (at natural abundance)
relative receptivity as compared to 13C:
2.16 (at natural abundance)Reference compound:
(conditions)Solution of 1% Tetramethylsilane (Si(CH3)4) in Chloroform-d (CDCl3).Frequency ratio:Ξ(29Si) = 19.867187 % [based on the reference substance] Among the natural silicon isotopes, only silicon-29 possesses a nucleus suitable for nuclear magnetic resonance (NMR), exhibiting low sensitivity and a large chemical shift range at a spin of 1/2. Silicon-29 NMR spectroscopy yields spectra with broad, sharp lines.
Isotones and Isobars
The following table shows the atomic nuclei that are isotonic (same neutron number N = 15) and isobaric (same nucleon number A = 29) with Silicon-29. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.
| Z | Isotone N = 15 | Isobar A = 29 |
|---|
| 5 | 20B | |
| 6 | 21C | |
| 7 | 22N | |
| 8 | 23O | |
| 9 | 24F | 29F |
| 10 | 25Ne | 29Ne |
| 11 | 26Na | 29Na |
| 12 | 27Mg | 29Mg |
| 13 | 28Al | 29Al |
| 14 | 29Si | 29Si |
| 15 | 30P | 29P |
| 16 | 31S | 29S |
| 17 | 32Cl | 29Cl |
| 18 | 33Ar | 29Ar |
| 19 | 34K | |
| 20 | 35Ca | |
| 21 | 36Sc | |
External data and identifiers
Literature and References
[1] - F. W. Aston:
The Constitution of the Elements.
In: Nature, 105, 547, (1920), DOI 10.1038/105547a0.
[2] - Markus Bursch et al.:
Comprehensive Benchmark Study on the Calculation of 29Si NMR Chemical Shifts.
In: Inorganic Chemistry, 60, 1, (2020), DOI 10.1021/acs.inorgchem.0c02907.
Last update: 2025-12-24
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