Silicon-32

Properties and data of the isotope ³²Si.

Contents

General Data

Radioactive Decay

Parent Nuclides

Occurrence

Isotones und Isobares

Literature

Silicon-32 is a radioisotope of the chemical element silicon, which has 18 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 32. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ³²Si serves exclusively academic purposes, experimental research and dating.

The discovery of the radioactive isotope was reported in 1953. According to this report, silicon-32 was formed by irradiating sodium chloride with a 340 MeV proton beam [1].

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

General data

Name of the isotope:Silicon-32; Si-32Symbol:³²Si or 3214SiMass number A:32 (= number of nucleons)Atomic number Z:14 (= number of protons)Neutrons N:18Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1.2857142857143 (= neutron-proton ratio)Neutron excess (N-Z):4Isotopic mass:31.9741515(3) u (atomic weight of Silicon-32)Nuclide mass:31.9664715 u (calculated nuclear mass without electrons)Mass excess:-24.07772 MeVMass defect:0.29136743600001 u (per nucleus)Nuclear binding energy:271.40701843 MeV (per nucleus)
8.48146933 MeV (average binding energy per nucleon)Separation energy:S_N = 9.2000(3) MeV (first neutron)
S_P = 16.4160(23) MeV (first proton)Half-life:157(7) aDecay constant λ:1.399043176199 × 10^-10 s^-1Specific activity α:2717817766518.6 Bq g^-1
73.454534230232 Ci g^-1Spin and parity:
(nuclear angular momentum)0+Mirror nucleus:Argon-32Year of discovery:1953

Radioactive Decay

Silicon-32 is a pure β-^- emitter that decays radioactively to phosphorus-32 free of gamma radiation by emitting high-energy electrons and neutrinos.

Half-life T_½ = 157(7) a respectively 4.954437378 × 10⁹ seconds s.

Decay mode	Daughter	Probability	Decay energy	Details	γ energy (intensity)
β^-	³²P	100 %	0.2272(3) MeV	β^-: 0.06955(11) MeV [100 %] v: 0.1581(2) MeV

Parent Nuclides

Direct parent isotopes are: ³²Al, ³³Al.

Occurrence

Silicon-32 is a cosmogenic nuclide that is formed in the upper atmosphere predominantly by the bombardment of argon-40 with cosmic radiation, which is then deposited on the Earth´s surface and thus occurs naturally in trace amounts.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 18) and isobaric (same nucleon number A = 32) with Silicon-32. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 18	Isobar A = 32
7	²⁵N
8	²⁶O
9	²⁷F
10	²⁸Ne	³²Ne
11	²⁹Na	³²Na
12	³⁰Mg	³²Mg
13	³¹Al	³²Al
14	³²Si	³²Si
15	³³P	³²P
16	³⁴S	³²S
17	³⁵Cl	³²Cl
18	³⁶Ar	³²Ar
19	³⁷K	³²K
20	³⁸Ca
21	³⁹Sc
22	⁴⁰Ti
23	⁴¹V
24	⁴²Cr
25	⁴³Mn

External data and identifiers

Adopted Levels, Gammas:NuDat 32Si

Literature and References

[1] - Manfred Lindner:
New Nuclides Produced in Chlorine Spallation.
In: Physical Review, 91, 642, (1953), DOI 10.1103/PhysRev.91.642.

[2] - Karsten Kossert et al.:
Activity standardization of ³²Si at PTB.
In: Applied Radiation and Isotopes, 202, 111042, (2023), DOI 10.1016/j.apradiso.2023.111042.