Isotopes of silicon

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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 170 years (0.21 MeV), and it decays by beta emission to 32P (which has a 14.28 day half-life [1]) 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 standard atomic mass is 28.0855(3) u. 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[edit]

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 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[edit]

  • The precision of the isotope abundances and atomic mass is limited through variations. The given ranges should be applicable to any normal terrestrial material.
  • Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses.
  • Uncertainties are given in concise form in parentheses after the corresponding last digits. Uncertainty values denote one standard deviation, except isotopic composition and standard atomic mass from IUPAC which use expanded uncertainties.
  • Blank spaces in the "natural abundance" and "range of natural variation" column show that the isotope discussed in the corresponding row is synthetic.

References[edit]

  1. ^ http://www.nucleonica.net/unc.aspx

External links[edit]


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