Silicon-28

Properties and data of the isotope ²⁸Si.

Contents

General Data

Parent Nuclides

Formation

Isotones und Isobares

Literature

Silicon-28 is a naturally occurring, stable isotope of the chemical element silicon, which has 14 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 28.

Silicon-28 was first identified as a distinct isotope in 1920 by measuring its mass spectrum [1].

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

General data

Name of the isotope:Silicon-28; Si-28Symbol:²⁸Si or 2814SiMass number A:28 (= number of nucleons)Atomic number Z:14 (= number of protons)Neutrons N:14Nucleon pairing (Z - N):even - evenNuclear ratio (N/Z ratio):1 (= neutron-proton ratio)Neutron excess (N-Z):0Isotopic mass:27.9769265344(6) u (atomic weight of Silicon-28)Nuclide mass:27.9692465 u (calculated nuclear mass without electrons)Mass excess:-21.49279 MeVMass defect:0.2539327376 u (per nucleus)Nuclear binding energy:236.53682148 MeV (per nucleus)
8.44774362 MeV (average binding energy per nucleon)Separation energy:S_N = 17.17961(11) MeV (first neutron)
S_P = 11.58490(5) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)0+Charge radius:3.1224(23) femtometer fmYear of discovery:1920

Parent Nuclides

Direct parent isotopes are: ²⁸P, ²⁸Al, ²⁹S, ³¹Ar, ³²Cl.

Formation

Silicon-28 is produced in stars through the so-called alpha process and the oxygen-burning process; at the same time, the nuclide drives the silicon-burning process in massive stars shortly before their supernova explosion. High-purity Si-28 – such as that used in quantum computers – can be obtained by various methods, as the review article [2] shows.

Occurrence

Comparison of the natural Silicon isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Silicon Isotopic mixture	28.085 u	100 %
Isotope ²⁸Si	27.9769265344(6) u	92.254 % [92.191 - 92.318 %]	stable	0+
Isotope ²⁹Si	28.9764946643(6) u	4.673 % [4.645 - 4.699 %]	stable	1/2+
Isotope ³⁰Si	29.973770137(23) u	3.073 % [3.037 - 3.110 %]	stable	0+

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 14) and isobaric (same nucleon number A = 28) with Silicon-28. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 14	Isobar A = 28
5	¹⁹B
6	²⁰C
7	²¹N
8	²²O	²⁸O
9	²³F	²⁸F
10	²⁴Ne	²⁸Ne
11	²⁵Na	²⁸Na
12	²⁶Mg	²⁸Mg
13	²⁷Al	²⁸Al
14	²⁸Si	²⁸Si
15	²⁹P	²⁸P
16	³⁰S	²⁸S
17	³¹Cl	²⁸Cl
18	³²Ar
19	³³K
20	³⁴Ca