Silicon-31

Properties and data of the isotope ³¹Si.

Contents

General Data

Radioactive Decay

Parent Nuclides

Isotones und Isobares

Literature

Silicon-31 is a radioisotope of the chemical element silicon, which has 17 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 31. The very short-lived, only artificially produced, unstable and thus radioactive nuclide has no practical significance; the study of ³¹Si is exclusively for academic purposes and experimental research.

According to a report from 1934, the radioactive nuclide was first produced and identified by irradiating natural phosphorus-31 with neutrons [1]:

³¹P(n,p)³¹Si.

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

General data

Name of the isotope:Silicon-31; Si-31Symbol:³¹Si or 3114SiMass number A:31 (= number of nucleons)Atomic number Z:14 (= number of protons)Neutrons N:17Nucleon pairing (Z - N):even - oddNuclear ratio (N/Z ratio):1.2142857142857 (= neutron-proton ratio)Neutron excess (N-Z):3Isotopic mass:30.97536320(5) u (atomic weight of Silicon-31)Nuclide mass:30.9676832 u (calculated nuclear mass without electrons)Mass excess:-22.94903 MeVMass defect:0.28149082 u (per nucleus)Nuclear binding energy:262.20700989 MeV (per nucleus)
8.45829064 MeV (average binding energy per nucleon)Separation energy:S_N = 6.58739(4) MeV (first neutron)
S_P = 14.3739(19) MeV (first proton)Half-life:157.24(20) minDecay constant λ:7.347330724612 × 10^-5 s^-1Specific activity α:1.474888685605 × 10⁺¹⁸ Bq g^-1
39861856.367711 Ci g^-1Spin and parity:
(nuclear angular momentum)3/2+Mirror nucleus:Chlorine-31Year of discovery:1934

Radioactive Decay

Half-life T_½ = 157.24(20) min respectively 9.434 × 10³ seconds s.

Decay mode	Daughter	Probability	Decay energy	γ energy (intensity)
β^-	³¹P	100 %	1.49151(4) MeV	1266.2(14) keV 0.0554(7) %

Parent Nuclides

Direct parent isotope is: ³¹Al.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 17) and isobaric (same nucleon number A = 31) with Silicon-31. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

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

External data and identifiers

Adopted Levels, Gammas:NuDat 31Si

Literature and References

[1] - Enrico Fermi, Edoardo Amaldi, O. D'Agostino, F. Rasetti, E. Segrè:
Artificial radioactivity produced by neutron bombardment.
In: Proceedings of the Royal Society A, 146, 857, (1934), DOI 10.1098/rspa.1934.0168.