Isotopes of silicon

Silicon (₁₄Si) has 23 known isotopes, with mass numbers ranging from 22 to 44. 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 (with decay energy 0.21 MeV), and it decays by beta emission to ³²P (which has a 14.28-day half-life)[2] 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.

A chart showing the relative abundances of the naturally occurring isotopes of silicon.

Main isotopes of silicon (₁₄Si)

Iso­tope Decay abun­dance half-life (t1/2) mode pro­duct ^28Si 92.2% stable ^29Si 4.7% stable ^30Si 3.1% stable ^31Si trace 2.62 h β^− ^31P ^32Si trace 153 y β^− ^32P
Standard atomic weight Ar, standard(Si)	[28.084, 28.086][1] Conventional: 28.085

List of isotopes

Nuclide[3] [n 1]	Z	N	Isotopic mass (Da)[4] [n 2][n 3]	Half-life [n 4]	Decay mode [n 5]	Daughter isotope [n 6]	Spin and parity [n 7][n 4]	Natural abundance (mole fraction)
	Excitation energy							Normal proportion	Range of variation
^22Si	14	8	22.03579(54)#	29(2) ms	β^+ (67.6%)	^22Al	0+
					β^+, p (32.4%)	^21Mg
^23Si	14	9	23.02544(54)#	42.3(4) ms	β^+ (12%)	^23Al	3/2+#
					β^+, p (88%)	^21Mg
^24Si	14	10	24.011535(21)	140(8) ms	β^+ (62.4%)	^24Al	0+
					β^+, p (37.6%)	^23Mg
^25Si	14	11	25.004109(11)	220(3) ms	β^+ (64.8%)	^25Al	5/2+
					β^+, p (35.2%)	^24Mg
^26Si	14	12	25.9923338(12)	2.2453(7) s	β^+	^26Al	0+
^27Si	14	13	26.98670469(12)	4.15(4) s	β^+	^27Al	5/2+
^28Si	14	14	27.9769265350(5)	Stable			0+	0.92223(19)	0.92205–0.92241
^29Si	14	15	28.9764946653(6)	Stable			1/2+	0.04685(8)	0.04678–0.04692
^30Si	14	16	29.973770137(23)	Stable			0+	0.03092(11)	0.03082–0.03102
^31Si	14	17	30.97536319(5)	157.36(26) min	β^−	^31P	3/2+
^32Si	14	18	31.9741515(3)	153(19) y	β^−	^32P	0+	trace	cosmogenic
^33Si	14	19	32.9779770(8)	6.18(18) s	β^−	^33P	(3/2+)
^34Si	14	20	33.978575(15)	2.77(20) s	β^−	^34P	0+
^34mSi	4256.1(4) keV			<210 ns	IT	^34Si	(3−)
^35Si	14	21	34.98455(4)	780(120) ms	β^− (94.74%)	^35P	7/2−#
^36Si	14	22	35.98665(8)	450(60) ms	β^− (87.5%)	^36P	0+
					β^−, n (12.5%)	^35P
^37Si	14	23	36.99295(12)	90(60) ms	β^− (83%)	^37P	(7/2−)#
					β^−, n (17%)	^36P
^38Si	14	24	37.99552(11)	90# ms [>1 μs]	β^−, n	^37P	0+
					β^−	^38P
^39Si	14	25	39.00249(15)	47.5(20) ms	β^−	^39P	7/2−#
^40Si	14	26	40.00583(37)	33.0(10) ms	β^−	^40P	0+
^41Si	14	27	41.01301(60)	20.0(25) ms	β^−	^41P	7/2−#
^42Si	14	28	42.01768(54)#	12.5(35) ms	β^−	^42P	0+
^43Si	14	29	43.02480(64)#	15# ms [>260 ns]			3/2−#
^44Si	14	30	44.03061(64)#	10# ms			0+

1. ^mSi – Excited nuclear isomer.
2. ( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
3. # – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
4. # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).
5. Modes of decay:

   IT:	Isomeric transition
   n:	Neutron emission
   p:	Proton emission

6. Bold symbol as daughter – Daughter product is stable.
7. ( ) spin value – Indicates spin with weak assignment arguments.

References

1. Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
2. Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
3. Half-life, decay mode, nuclear spin, and isotopic composition is sourced in:
   Audi, G.; Kondev, F. G.; Wang, M.; Huang, W. J.; Naimi, S. (2017). "The NUBASE2016 evaluation of nuclear properties" (PDF). Chinese Physics C. 41 (3): 030001. Bibcode:2017ChPhC..41c0001A. doi:10.1088/1674-1137/41/3/030001.
4. Wang, M.; Audi, G.; Kondev, F. G.; Huang, W. J.; Naimi, S.; Xu, X. (2017). "The AME2016 atomic mass evaluation (II). Tables, graphs, and references" (PDF). Chinese Physics C. 41 (3): 030003-1–030003-442. doi:10.1088/1674-1137/41/3/030003.

External links

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