Isotopes of silicon
Encyclopedia
Silicon
(Si) has 24 known isotope
s, with mass number
s 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 http://sciencegateway.org/isotope/phosp32.html) 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.
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
(Si) has 24 known isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s, with mass number
Mass number
The mass number , also called atomic mass number or nucleon number, is the total number of protons and neutrons in an atomic nucleus. Because protons and neutrons both are baryons, the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion...
s 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
Cosmic ray spallation
Cosmic ray spallation is a form of naturally occurring nuclear fission and nucleosynthesis. It refers to the formation of elements from the impact of cosmic rays on an object. Cosmic rays are highly energetic charged particles from outside of Earth ranging from protons, alpha particles, and nuclei...
of argon
Argon
Argon is a chemical element represented by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is the third most common gas in the Earth's atmosphere, at 0.93%, making it more common than carbon dioxide...
. Its half-life
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
has been determined to be approximately 170 years (0.21 MeV), and it decays by beta emission
Beta decay
In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a...
to 32P
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
(which has a 14.28 day half-life http://sciencegateway.org/isotope/phosp32.html) and then to 32S
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
. 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.
Table
| nuclide symbol |
Z(p Proton The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number.... ) |
N(n Neutron The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of... ) |
isotopic mass (u) |
half-life | decay mode(s) | daughter isotope(s)Bold for stable isotopes |
nuclear spin |
representative isotopic composition (mole fraction) |
range of natural variation (mole fraction) |
|---|---|---|---|---|---|---|---|---|---|
| 22Si | 14 | 8 | 22.03453(22)# | 29(2) ms | β+ Beta decay In nuclear physics, beta decay is a type of radioactive decay in which a beta particle is emitted from an atom. There are two types of beta decay: beta minus and beta plus. In the case of beta decay that produces an electron emission, it is referred to as beta minus , while in the case of a... (68%) |
22Al | 0+ | ||
| β+, p Proton emission Proton emission is a type of radioactive decay in which a proton is ejected from a nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, in which case the process is known as beta-delayed proton emission, or can occur from the ground state of very... (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) | 170 y | β− | 32P | 0+ | trace Trace radioisotope A trace radioisotope is a radioisotope that occurs naturally in trace amounts . Generally speaking, trace radioisotopes have half-lives that are short in comparison to the age of the earth, since primordial nuclides tend to occur in larger than trace amounts... |
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 Neutron emission Neutron emission is a type of radioactive decay of atoms containing excess neutrons, in which a neutron is simply ejected from the nucleus. Two examples of isotopes which emit neutrons are helium-5 and beryllium-13... (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− | 36P | ||||||||
| 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+ | ||||