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 [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 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)	daughter isotope(s)	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+

Notes

• 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

• Isotope masses from:
• Isotopic compositions and standard atomic masses from:
• Half-life, spin, and isomer data selected from the following sources. See editing notes on this article's talk page.

External links

• Silicon isotopes data from The Berkeley Laboratory Isotopes Project's

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