Isotopes of silicon

Silicon (Si) has 24 known isotopes, with mass numbers ranging from 22 to 45. 28Si (the most abundant isotope, at 92.23%), 29Si (4.67%), and 30Si (3.1%) are stable. The longest-lived radioisotope is 32Si, which is produced by cosmic ray spallation of argon. Its half-life has been determined to be approximately 150 years (0.21 MeV), and it decays by beta emission to 32P (which has a 14.28 day half-life ) and then to 32S. After 32Si, 31Si has the second longest half-life at 157.3 minutes. All others have half-lives under 7 seconds. The relative atomic mass is 28.0855(3). The least stable is usually 43Si with a half-life greater than 60 nanoseconds.

A chart showing the relative abundances of the naturally-occurring isotopes of Silicon.

Table

nuclide
symbol
Z(p) N(n)  
isotopic mass (u)
 
half-life decay mode(s)[1] daughter
isotope(s)[n 1]
nuclear
spin
representative
isotopic
composition
(mole fraction)
range of natural
variation
(mole fraction)
22Si 14 8 22.03453(22)# 29(2) ms β+ (68%) 22Al 0+
β+, p (32%) 21Mg
23Si 14 9 23.02552(21)# 42.3(4) ms β+ 23Al 3/2+#
24Si 14 10 24.011546(21) 140(8) ms β+ (92%) 24Al 0+
β+, p (8%) 23Mg
25Si 14 11 25.004106(11) 220(3) ms β+ (63.19%) 25Al 5/2+
β+, p (36.8%) 24Mg
26Si 14 12 25.992330(3) 2.234(13) s β+ 26Al 0+
27Si 14 13 26.98670491(16) 4.16(2) s β+ 27Al 5/2+
28Si 14 14 27.9769265325(19) Stable 0+ 0.92223(19) 0.92205–0.92241
29Si 14 15 28.976494700(22) Stable 1/2+ 0.04685(8) 0.04678–0.04692
30Si 14 16 29.97377017(3) Stable 0+ 0.03092(11) 0.03082–0.03102
31Si 14 17 30.97536323(4) 157.3(3) min β 31P 3/2+
32Si 14 18 31.97414808(5) 153(19) y β 32P 0+ trace cosmogenic
33Si 14 19 32.978000(17) 6.18(18) s β 33P (3/2+)
34Si 14 20 33.978576(15) 2.77(20) s β 34P 0+
35Si 14 21 34.98458(4) 780(120) ms β (94.74%) 35P 7/2−#
β, n (5.26%) 34P
36Si 14 22 35.98660(13) 0.45(6) s β (88%) 36P 0+
β, n (12%) 35P
37Si 14 23 36.99294(18) 90(60) ms β (83%) 37P (7/2−)#
β, n (17%) 36P
38Si 14 24 37.99563(15) 90# ms [>1 µs] β, n 37P 0+
β 38P
39Si 14 25 39.00207(36) 47.5(20) ms β 39P 7/2−#
40Si 14 26 40.00587(60) 33.0(10) ms β 40P 0+
41Si 14 27 41.01456(198) 20.0(25) ms β 41P 7/2−#
42Si 14 28 42.01979(54)# 13(4) ms β 42P 0+
43Si 14 29 43.02866(75)# 15# ms [>260 ns] 3/2−#
44Si 14 30 44.03526(86)# 10# ms 0+
  1. Bold for stable isotopes

Notes

References

  1. "Universal Nuclide Chart". nucleonica. (registration required (help)).

External links

Isotopes of aluminium Isotopes of silicon Isotopes of phosphorus
Table of nuclides
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