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Silicon-22

Properties and data of the isotope 22Si.


Contents

 

Silicon-22 isotope

Silicon-22 is a radioisotope of the chemical element silicon, which has 8 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 22. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of 22Si is exclusively for academic purposes and experimental research.

The radioactive nuclide was first observed and identified during the fragmentation of a nickel template by irradiation with argon-36 ions of an energy of 86 MeV/u [1].

See also: List of individual Silicon isotopes (and general data sources).

 

General data

Name of the isotope:Silicon-22; Si-22Symbol:22Si or 2214SiMass number A:22 (= number of nucleons)Atomic number Z:14 (= number of protons)Neutrons N:8Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):0.57142857142857 (= neutron-proton ratio)Neutron excess (N-Z):-6Isotopic mass:22.03611(54) u (atomic weight of Silicon-22)Nuclide mass:22.02843 u (calculated nuclear mass without electrons)Mass excess:33.63625 MeVMass defect:0.142759776 u (per nucleus)Nuclear binding energy:132.97987479 MeV (per nucleus)
6.04453976 MeV (average binding energy per nucleon)
Separation energy:
SP = 0.739(781) MeV (first proton)
Half-life:28.7(11) msDecay constant λ:24.151469705921 s-1Specific activity α:6.611070570161 × 10+23 Bq g-1
17867758297734 Ci g-1
Spin and parity:
(nuclear angular momentum)
0+Mirror nucleus:Oxygen-22Year of discovery:1987

 

Radioactive Decay

Half-life T½ = 28.7(11) ms respectively 2.87 × 10-2 seconds s.

Decay
mode
DaughterProbabilityDecay energyγ energy
(intensity)
EC/β+22Al37.3 %15.439(641) MeV
β+, p21Mg62(5) %
β+, 2p20Na0.7(3) %

 

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 8) and isobaric (same nucleon number A = 22) with Silicon-22. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

 

ZIsotone N = 8Isobar A = 22
210He
311Li
412Be
513B
614C22C
715N22N
816O22O
917F22F
1018Ne22Ne
1119Na22Na
1220Mg22Mg
1321Al22Al
1422Si22Si

 

External data and identifiers

Adopted Levels, Gammas:NuDat 22Si

 

Literature and References

[1] - M. G. Saint-Laurent et al.:
Observation of a bound TZ=-3 nucleus: 22Si.
In: Physical Review, 59, 33, (1987), DOI 10.1103/PhysRevLett.59.33.

[2] - X.X. Xu et al.:
Observation of β-delayed two-proton emission in the decay of 22Si.
In: Physics Letters B, 766, (2017), DOI 10.1016/j.physletb.2017.01.028.

[3] - Y. M. Xing et al.:
Z = 14 Magicity Revealed by the Mass of the Proton Dripline Nucleus 22Si.
In: Physical Review Letters, 135, 012501, (2025), DOI 10.1103/ffwt-n7yc.

 


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Last update: 2025-12-23


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