Notation: mass number as a left superscript (e.g., ³¹Si).
Columns: Isotope | Z | A | Stable? | Half‑life | Decay mode(s) | Daughter | Radiation | Origin | Uses | Notes.
Scope: Silicon has 3 stable nuclides (²⁸Si, ²⁹Si, ³⁰Si) and 22 radioisotopes from ²²Si to ⁴⁶Si (many very short‑lived); key values from NUBASE/AME as compiled in the evaluated table. (Wikipedia)
| Isotope | Z | A | Stable? | Half‑life | Decay mode(s) | Daughter | Radiation | Origin | Uses | Notes |
|---|---|---|---|---|---|---|---|---|---|---|
| ²²Si | 14 | 22 | Unstable | 28.7(11) ms | β⁺p 62%; β⁺ 37%; β⁺2p 0.7% | ²¹Mg; ²²Al; ²⁰Na | β⁺; delayed p/2p | Synthetic | Dripline/β‑delayed‑p studies | Branching per evaluation. (Wikipedia) |
| ²³Si | 14 | 23 | Unstable | 42.3(4) ms | β⁺p 88%; β⁺ 8%; β⁺2p 3.6% | ²²Mg; ²³Al; ²¹Na | β⁺; delayed p/2p | Synthetic | β‑delayed‑p statistics | — (Wikipedia) |
| ²⁴Si | 14 | 24 | Unstable | 143.2(21) ms | β⁺ 65.5%; β⁺p 34.5% | ²⁴Al; ²³Mg | β⁺; delayed p | Synthetic | Structure tests | — (Wikipedia) |
| ²⁵Si | 14 | 25 | Unstable | 220.6(10) ms | β⁺ 65%; β⁺p 35% | ²⁵Al; ²⁴Mg | β⁺; delayed p | Synthetic | Reaction studies | — (Wikipedia) |
| ²⁶Si | 14 | 26 | Unstable | 2.2453(7) s | β⁺ | ²⁶Al | β⁺ | Synthetic | β⁺ standard; trapping | — (Wikipedia) |
| ²⁷Si | 14 | 27 | Unstable | 4.117(14) s | β⁺ | ²⁷Al | β⁺ | Synthetic | β⁺ spectroscopy | — (Wikipedia) |
| ²⁸Si | 14 | 28 | Stable | stable | — | — | — | Natural | Ultra‑enriched ²⁸Si for quantum computing; Avogadro sphere (metrology) | ²⁸Si enrichment reduces decoherence; Avogadro project. (Wikipedia) |
| ²⁹Si | 14 | 29 | Stable | stable | — | — | — | Natural | NMR/EPR label (I = 1/2) | Only MR‑active stable Si nuclide. (Wikipedia) |
| ³⁰Si | 14 | 30 | Stable | stable | — | — | — | Natural | Isotope geochemistry; targets for activation | — (Wikipedia) |
| ³¹Si | 14 | 31 | Unstable | 157.16(20) min | β⁻ → ³¹P (100%) | ³¹P | β⁻ | Activation product (n,γ on ³⁰Si) | Neutron activation analysis (NAA) | MIRD/NUBASE concordance on t½. (Wikipedia, MIRDSoft) |
| ³²Si | 14 | 32 | Unstable | 157(7) y | β⁻ → ³²P → ³²S | ³²P (→ ³²S) | β⁻ (no γ in chain) | Natural trace (cosmogenic) & synthetic | Geochronology, hydrology; low‑level tracer | Reported values range ~153–159 y; we adopt NUBASE2020 157(7) y. (Wikipedia, National Isotope Development Center, Astrophysics Data System) |
| ³³Si | 14 | 33 | Unstable | 6.18(18) s | β⁻ | ³³P | β⁻ | Synthetic | β‑decay studies | — (Wikipedia) |
| ³⁴Si | 14 | 34 | Unstable | 2.77(20) s | β⁻ | ³⁴P | β⁻ | Synthetic | Doubly‑magic‑like Z=14/N=20 case; bubble‑like proton density | ³⁴mSi isomer (<210 ns, IT). (Wikipedia) |
| ³⁵Si | 14 | 35 | Unstable | 780(120) ms | β⁻ (± n?) | ³⁵P (…³⁴P) | β⁻; delayed n? | Synthetic | Structure | β‑delayed n tentative. (Wikipedia) |
| ³⁶Si | 14 | 36 | Unstable | 503(2) ms | β⁻ 88%; β⁻n 12% | ³⁶P; ³⁵P + n | β⁻; delayed n | Synthetic | β‑delayed‑n benchmarks | — (Wikipedia) |
| ³⁷Si | 14 | 37 | Unstable | 141.0(35) ms | β⁻ 83%; β⁻n 17%; (β⁻2n?) | ³⁷P; ³⁶P (+ n) | β⁻; delayed n | Synthetic | Continuum studies | — (Wikipedia) |
| ³⁸Si | 14 | 38 | Unstable | 63(8) ms | β⁻ 75%; β⁻n 25% | ³⁸P; ³⁷P + n | β⁻; delayed n | Synthetic | Dripline approach | — (Wikipedia) |
| ³⁹Si | 14 | 39 | Unstable | 41.2(41) ms | β⁻ 67%; β⁻n 33%; (β⁻2n?) | ³⁹P; ³⁸P (+ n) | β⁻; delayed n | Synthetic | β‑delayed‑n statistics | — (Wikipedia) |
| ⁴⁰Si | 14 | 40 | Unstable | 31.2(26) ms | β⁻ 62%; β⁻n 38%; (β⁻2n?) | ⁴⁰P; ³⁹P (+ n) | β⁻; delayed n | Synthetic | Shell evolution | — (Wikipedia) |
| ⁴¹Si | 14 | 41 | Unstable | 20.0(25) ms | β⁻n > 55%; β⁻ < 45%; (β⁻2n?) | ⁴⁰P; ⁴¹P; (…³⁹P) | β⁻; delayed n | Synthetic | Structure | Branching split per evaluation. (Wikipedia) |
| ⁴²Si | 14 | 42 | Unstable | 15.5(4stat) / 16(sys) ms | β⁻ 51%; β⁻n 48%; β⁻2n 1% | ⁴²P; ⁴¹P; ⁴⁰P | β⁻; delayed n/2n | Synthetic | N=28 shell anomaly; first FRIB half‑life set | FRIB half‑life measurement 2022. (Wikipedia) |
| ⁴³Si | 14 | 43 | Unstable | 13(4stat) / 2(sys) ms | β⁻n 52%; β⁻ 27%; β⁻2n 21% | ⁴²P; ⁴³P; ⁴¹P | β⁻; delayed n/2n | Synthetic | Neutron‑rich systematics | FRIB result. (Wikipedia) |
| ⁴⁴Si | 14 | 44 | Unstable | ~4 ms (#; > 360 ns) | β⁻? (± β⁻n/β⁻2n?) | ⁴⁴P (…⁴³/⁴²P) | β⁻; delayed n? | Synthetic | Edge‑of‑stability tests | Trend‑estimated; sparse data. (Wikipedia) |
| ⁴⁵Si | 14 | 45 | Unstable | ~4 ms (#) | β⁻? | ⁴⁵P | β⁻ | Synthetic | Newly discovered (2024) | Discovery reported 2024; properties limited. (Wikipedia) |
| ⁴⁶Si | 14 | 46 | Unstable | (not yet established) | β⁻? | ⁴⁶P | β⁻ (expected) | Synthetic | Newly discovered (2024) | Observation reported; t½ pending publication. (Wikipedia) |
Radiation key: β⁺/EC → annihilation γ (511 keV); β⁻ (electron); β⁻n / β⁻2n = β‑decay with 1 or 2 delayed neutrons; p/2p = prompt proton(s) from proton‑unbound branches.
Natural/Applied highlights: ²⁸Si ultra‑enrichment for quantum devices; ²⁹Si for NMR/EPR; ³¹Si for NAA; ³²Si (cosmogenic) for geochronology/hydrology with ³²P daughter; the rest are research nuclides. (Wikipedia, MIRDSoft, National Isotope Development Center)
Totals — Silicon
- Stable3 (²⁸Si, ²⁹Si, ³⁰Si)
- Unstable22 (²²–²⁷Si, ³¹–⁴⁶Si)
- Total isotopes25. (Wikipedia)
Running cumulative totals (H → Si, Z = 1…14)
- Cumulative total isotopes229 (through Al: 204 • Si: +25)
- Cumulative stable28 (through Al: 25 • Si: +3)
- Cumulative unstable201
Sources
- Isotopes of silicon — evaluated per‑nuclide table (half‑lives, modes/branching, daughters); cites NUBASE2020/AME2020 and FRIB results. (Wikipedia)
- 28Si/29Si applications — quantum‑computing‑grade ²⁸Si enrichment; ²⁹Si as the only MR‑active stable Si. (Wikipedia)
- 31Si dosimetry/decay — MIRD datasheet (157.3 min, β⁻ → ³¹P). (MIRDSoft)
- 32Si half‑life and use — NIDC product sheet (153 y to ³²P) and dissertation work (≈159 y); table adopts NUBASE value 157(7) y. (National Isotope Development Center, Astrophysics Data System, Wikipedia)
- Neutron‑rich frontier — FRIB half‑lives for ⁴²–⁴³Si; discovery of ⁴⁵,⁴⁶Si (PTEP 2024). (Wikipedia)
Next: Phosphorus — P (Z = 15)
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