Skip to Main Content

About Silicon

Silicon Bohr

Silicon is truly ubiquitous, but is almost never found as the free element in nature. Instead, it occurs mostly as silicon dioxide, more commonly known as sand or quartz, or in silicate minerals, generally in the found in the forms of clay or rock. It was first proposed that silica sand was likely the oxide of a previously unknown element by Antoine Lavoisier in 1787. In 1808, Sir Humphry Davy named this hypothetical element “silicium”, combining the Latin silex, meaning stone, with the traditional -ium ending often given to metallic elements. The name was changed to silicon in 1817, as the -on ending suggested its closer relation to the non-metallic elements boron and carbon, but it wasn’t until 1823 that the Swedish chemist Jons Jacob Berzelius finally succeeded in preparing pure amorphous silicon and as the first to do so was given credit for “discovering” the element.

The vast majority of silicon used commercially is never separated out of the materials in which it occurs naturally, which are often processed fairly minimally before use. Silicate clays are used to produce whiteware ceramics such as porcelain and in the making of ceramic bricks and cement used as building materials. Silicate-containing rock such as granite is used directly in structural and decorative applications, and silica sand mixed with gravel and cement produces concrete. Sand is also used widely as an abrasive and as a filler in plastics, rubber, and paints. Additionally, diatomaceous earth, a form of silica rock consisting of fossilized remains of diatoms, has many direct commercial applications, especially as an absorbent, a filtration medium, a mild abrasive, and a natural pesticide.

More refined silicon products account for a much smaller portion of commercial silicon usage, but nonetheless are extremely important economically. Common silica sand is the starting point for production of a variety of refined silica products, other silicon compounds, silicon-containing alloys, and elemental silicon at various levels of purity, all of which play significant roles in industry. The following paragraphs give an overview of the major categories of silicon end uses, but do not constitute an exhaustive list.

Silicon in Alloys

Silicon is commonly used as an alloying element. Silica sand is reduced with carbon in the presence of iron to produce ferrosilicon, which can then be used in silicon-containing steels. In molten iron, silicon aids in maintaining carbon content within narrow limits required for a given steel grade. Used in larger amounts, as in electrical steel, silicon favorably influences resistivity and ferromagnetic properties of the material.

For use in non-ferrous alloys, metallurgical grade silicon is produced by reacting high-purity silica with carbon in an electric arc furnace. The most common non-ferrous silicon alloys are aluminum-silicon alloys. The appropriate proportions of aluminum and silicon produce a material that exhibits very little thermal contraction during solidification, making it ideal for casting applications. Metallurgical-grade silicon is also used as a minor alloying agent in a number of other alloys designed for specialized applications.

High-Strength Ceramics

First produced synthetically in the nineteenth century, silicon nitride has been known to science for about as long as silicon carbide, but nonetheless took a much slower path to commercial exploitation. The potential of silicon nitride as a refractory material was first recognized in the 1950s, and in fact the material came to be used as a binder in silicon carbide ceramics, a use which continues to some extent today. However, pure silicon nitride ceramics proved extremely difficult to fabricate, and early production methods either resulted in materials with less-than-ideal or unreliable mechanical properties, or used production methods that severely limited the types of parts that could be produced. Today, sintered silicon nitride ceramic components can be produced with excellent mechanical properties, but this requires extremely pure silicon nitride nanopowder and precisely controlled manufacturing conditions, both of which contribute to the high cost of this material. These materials have excellent shock resistance, and have come to be used in small engine components. Additionally, silicon nitride can be used to produce ball bearings that can tolerate corrosive environments, high operating temperatures, and low lubrication all while performing better and weighing less than alternatives.

Sialons, ceramics produced with aluminum oxide, silicon nitride and sometimes rare-earth oxides, were first developed in response to difficulties in producing sintered silicon nitride ceramics. Many variations on sialons exist, as variations in starting compositions as well as in production techniques can produce materials with vastly different properties, which result from differences in crystal structure. Some of these variations retain many of the desirable properties of silicon nitride while also providing the added benefit of easier production processes. Other variations are formulated to provide additional properties, such as electrical conductivity or resistance to damage in specific chemical environments. Currently, sialons are used primarily in cutting tools and industrial machine components subjected to extreme conditions.

The semiconductor properties of silicon carbide have been known since the early twentieth century, when the material found use in radio detectors and the first LEDs. However, these and several other uses were developed in the very early days of semiconductor devices, and alternative materials with properties more suited to these applications have since been developed, largely displacing silicon carbide from its historical functions. Research developing silicon carbide as a semiconductor has since explicitly focused on exploiting its strengths, which include its ability to perform at high temperatures and in strong electrical fields. These properties theoretically allow for the production of much smaller, faster, more energy efficient, and more heat-tolerant electronic devices than are possible with traditional silicon based technologies. Initially difficulties producing silicon carbide crystals without defects hampered development of sophisticated silicon carbide electronics, but functional silicon carbide diodes and transistors are now commercially available, and development of these technologies is ongoing.

Amorphous silicon nitride, which can be produced in thin layers using chemical vapor deposition, is an important material in integrated circuits manufacturing, where it is used as structurally as an electrical insulator or protective passivation layer, or as an etch mask in the machining process. Additionally, doped silicon nitrides are being investigated for use as a semiconductor in devices such as LEDs, and both silicon nitride and sialon can be doped to produce phosphors.

Silica glasses

In common usage, glass refers to soda-lime glass, a silica-based glass produced by melting quartz sand along with sodium carbonate, lime, dolmite, and aluminum oxide. This is the glass commonly used in window panes and beverage containers. Most other products commonly known as glass are also silica based, but have differing compositions intended to produce properties favorable for specific uses. For example, borosilicate glasses, often sold under the name Pyrex, contain boron oxide, are notable for their superior ability to withstand thermal shock, and are used for laboratory glassware, household cookware, and optical components. Aluminosilicate glass, another common variety, is used in the composite material fiberglass, and in shatter-resistant glass used for windshields of high-speed vehicles and, increasingly, exposed glass surfaces on portable electronic devices such as mobile phones.

Alternatively, glass can be produced from pure silicon dioxide with no other compounds added. The resulting material is known as fused quartz, and compared to soda lime glass is stronger, has better optical properties, and better resists thermal shock. It also melts at a much higher temperature. This property, though often desirable, makes it considerably more costly to produce than other types of glass. It is therefore used primarily for applications which require these improved properties, which include the production of precision optical components such as high-quality lenses and optical fibers, photolithography masks, and refractory materials for use in high-temperature laboratory and industrial processes.

Synthetic quartz

Quartz is a natural piezoelectric material that finds use in crystal oscillators used to mark time in clocks and digital devices, and to standardize frequency in radio frequency devices. Quartz for this use is generally produced synthetically from silica sand, as this allows for precision engineering of crystal properties.


Silicones are mixed organic-inorganic polymers generally consisting of a silicon-oxygen backbone connected to hydrocarbon side groups. Varying the hydrocarbon groups present, silicon-oxygen chain lengths, and the degree of crosslinking can produce a wide range of materials, from silicone oil lubricants to hard silicone resins, but all tend to exhibit low thermal conductivity, chemical reactivity, and toxicity. The wide range of consistencies possible and ease of fabrication, as well as their polymeric structure, prompts comparison to hydrocarbon-based plastics, and in household devices the materials are sometimes used interchangeably. However, the low toxicity and high heat stability of silicone products allow for a broader range of uses in cookware and medical devices. Silicones are additionally used for electrical and thermal insulation, adhesive, sealant, industrial lubricants, dry-cleaning solvent, and personal care products.

Ultra high purity silicon in electronics and photovoltaics

Despite the fact that wafer silicon used in semiconductor devices accounts for only a tiny fraction of the commercial use of the element, this single application is the one most intimately tied to public conceptions of silicon, as its influence on modern life has been profound. Though neither the first integrated circuits (germanium) nor the first solar cells (selenium) contained silicon, for most of the history of both industries, high-purity silicon has been the unquestionably dominant semiconductor material.

For integrated circuit applications, even tiny crystal defects interfere with tiny circuit paths, necessitating the use of monocrystalline silicon. This material is produced using the Czochralski crystal growth process, which requires slow growth of a single enormous crystal from molten high-purity silicon in a carefully controlled environment. Integrated circuits are build using thin wafers cut from these crystals, as are the highest efficiency silicon photovoltaic cells. Other semiconductor devices generally do not require monocrystalline silicon, but still require high-purity to control electrical properties of the material. High-purity amorphous or polycrystalline silicon is found in most silicon photovoltaic cells, and some other large area semiconductor devices.

Synthetic silica products

There are many forms of synthetic silicon oxide, including precipitated silica, colloidal silica, silica gel, fumed silica, and silica fume. Though each product is primarily silicon dioxide, each is produced as a result of a different industrial process, and they vary in particle size. Commonly, these products are employed as mild abrasive agents, anti-caking or thickening agents in food, absorbants, or as filler material in plastics, rubbers, silicones, or cement, though precise end uses vary by form.

Silica gel is the form of synthetic silica most familiar to consumers. These microporous silica beads are commonly found in small paper packets that included in packaging of variety of products to absorb excess moisture. The same absorption properties are exploited for use in cat litter. Silica gel is also used in chemistry laboratories as a stationary phase for chromatography or, when modified with covalently bound functional groups, as a reducing or chelating agent.

+ Open All
- Close All
Organosilicon & Organometallics

High Purity (99.999%) Silicon (Si) Sputtering Target Silica, as sand, is a principal ingredient of glass--a material with excellent mechanical, optical, thermal, and electrical properties. Ultra high purity silicon can be doped with boron, gallium, phosphorus, or arsenic to produce silicon for use in transistors, solar cells, rectifiers, and other solid-state High Purity (99.999%) Silicon Oxide (SiO2) Powder devices which are used extensively in the electronics industry. Silcones, a large family of synthetic polymers, are important products of silicon. These range from liquids to hard glass-like solids with many useful properties. Silicon is available as metal and compounds with purities from 99% to 99.999% (ACS grade to ultra-high purity). Elemental or metallic forms include pellets, rod, wire and granules for evaporation source material purposes. Silicon oxides are available in powder and dense pellet form for such uses as optical coating and thin film applications. Silicon fluoride is an insoluble silicon source for uses in which the oxide is undesirable such as metallurgy, chemical and physical vapor deposition and in some optical coatings. Silicon is also available in soluble forms including chlorides and acetates. These compounds can be manufactured as solutions at specified stoichiometries.

Silicon Properties

Silicon (Si) atomic and molecular weight, atomic number and elemental symbolSilicon is a Block P, Group 14, Period 3 element. The number of electrons in each of Silicon's shells is 2, 8, 4 and its electron configuration is [Ne] 3s2 3p2. The silicon atom has a radius of and its Van der Waals radius is In its elemental form, silicon's CAS number is 7440-21-3. Silicon Elemental Silicon makes up 25.7% of the earth's crust, by weight, and is the second most abundant element, exceeded only by oxygen.Silicon Bohr Molecule Silicon was discovered and first isolated by Jöns Jacob Berzelius in 1823. It is rarely found in pure crystal form and is usually produced from the iron-silicon alloy Ferrosilicon. The name Silicon originates from the Latin word "silex" which means flint or hard stone.

Symbol: Si
Atomic Number: 14
Atomic Weight: 28.09
Element Category: metalloid
Group, Period, Block: 14, 3, p
Color: dark gray with a bluish tinge
Other Names: Silicium, Silicio
Melting Point: 1414°C, 2577.2°F, 1687.15 K
Boiling Point: 3265°C, 5909°F, 3538.15 K
Density: 2330 kg/m3
Liquid Density @ Melting Point: 2.57 g·cm3
Density @ 20°C: 2.33 g/cm3
Density of Solid: 2330 kg·m3
Specific Heat: 0.168 Cal/g/K @ 25°C
Superconductivity Temperature: N/A
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 39.6
Heat of Vaporization (kJ·mol-1): 383.3
Heat of Atomization (kJ·mol-1): 451.29
Thermal Conductivity: 1.49 W/cm/K @ 298.2 K
Thermal Expansion: (25 °C) 2.6 µm·m-1·K-1
Electrical Resistivity: 3-4 µΩ-cm @ 0°C
Tensile Strength: N/A
Molar Heat Capacity: 19.789 J·mol-1·K-1
Young's Modulus: 51-80 GPa
Shear Modulus: N/A
Bulk Modulus: 97.6 GPa
Poisson Ratio: 0.064 - 0.28
Mohs Hardness: 7
Vickers Hardness: N/A
Brinell Hardness: N/A
Speed of Sound: (20 °C) 8433 m·s-1
Pauling Electronegativity: 1.9
Sanderson Electronegativity: 2.14
Allred Rochow Electronegativity: 1.74
Mulliken-Jaffe Electronegativity: 2.28 (sp3 orbital)
Allen Electronegativity: 1.916
Pauling Electropositivity: 2.1
Reflectivity (%): 28
Refractive Index: N/A
Electrons: 14
Protons: 14
Neutrons: 14
Electron Configuration: [Ne] 3s2 3p2
Atomic Radius: 111 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 111 pm
Covalent Radius (Å): 1.14
Van der Waals Radius: 210 pm
Oxidation States: 2, 4, -4
Phase: Solid
Crystal Structure: diamond cubic
Magnetic Ordering: diamagnetic
Electron Affinity (kJ·mol-1) 134.115
1st Ionization Energy: 786.52 kJ·mol-1
2nd Ionization Energy: 1577.15 kJ·mol-1
3rd Ionization Energy: 3231.61 kJ·mol-1
CAS Number: 7440-21-3
EC Number: 231-130-8
MDL Number: MFCD00085311
Beilstein Number: N/A
SMILES Identifier: [SiH4]
InChI Identifier: InChI=1S/Si
PubChem CID: 5461123
ChemSpider ID: 4574465
Earth - Total: 15.12%
Mercury - Total: 7.05%
Venus - Total: 15.82%
Earth - Seawater (Oceans), ppb by weight: 1000
Earth - Seawater (Oceans), ppb by atoms: 220
Earth -  Crust (Crustal Rocks), ppb by weight: 2.7E+08
Earth -  Crust (Crustal Rocks), ppb by atoms: 2E+08
Sun - Total, ppb by weight: 900000
Sun - Total, ppb by atoms: 40000
Stream, ppb by weight: 5000
Stream, ppb by atoms: 180
Meterorite (Carbonaceous), ppb by weight: 1.4E+08
Meterorite (Carbonaceous), ppb by atoms: 1E+08
Typical Human Body, ppb by weight: 260000
Typical Human Body, ppb by atom: 58000
Universe, ppb by weight: 700000
Universe, ppb by atom: 30000
Discovered By: Jöns Jacob Berzelius
Discovery Date: 1823
First Isolation: Jöns Jacob Berzelius (1823)

Health, Safety & Transportation Information for Silicon

Silicon is not toxic but can cause chronic respiratory problems if inhaled as a fine silica or silicate dust. Asbestos silicates are carcinogenic. Safety data for Silicon and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab. The below information applies to elemental Silicon.

Safety Data
Signal Word Warning
Hazard Statements H228
Hazard Codes F
Risk Codes 11
Safety Precautions 16-33-36
RTECS Number VW0400000
Transport Information UN 1346 4.1/PG 3
WGK Germany 2
Globally Harmonized System of
Classification and Labelling (GHS)
Review and Print SDS for Elemental Silicon


Date Created: 05/15/2015
Date Revised: 05/15/2015


Product Name: Silicon Metal

Product Number: All applicable American Elements product codes, e.g. SI-E-05-I, SI-E-05-L, SI-E-05-P, SI-E-05-ST, SI-E-05-WSX

CAS #: 7440-21-3

Relevant identified uses of the substance: Scientific research and development

Supplier details:
American Elements
1093 Broxton Ave. Suite 2000
Los Angeles, CA 90024
Tel: +1 310-208-0551
Fax: +1 310-208-0351

Emergency telephone number:
Domestic, North America +1 800-424-9300
International +1 703-527-3887


Classification of the substance or mixture
Classification according to Regulation (EC) No 1272/2008
The substance is not classified as hazardous to health or the environment according to the CLP regulation.
Classification according to Directive 67/548/EEC or Directive 1999/45/EC
Not applicable
Information concerning particular hazards for human and environment:
No information known.
Hazards not otherwise classified
No information known.
Label elements
Labelling according to Regulation (EC) No 1272/2008
Not applicable
Hazard pictograms
Not applicable
Signal word
Not applicable
Hazard statements
Not applicable
WHMIS classification
Not controlled
Classification system
HMIS ratings (scale 0-4)
(Hazardous Materials Identification System)

Health (acute effects) = 1
Flammability = 0
Physical Hazard = 0
Other hazards
Results of PBT and vPvB assessment
Not applicable.
Not applicable.


Chemical characterization: Substances
CAS# Description:
7440-21-3 Silicon
Identification number(s):
EC number:


Description of first aid measures
General information
No special measures required.
After inhalation
Seek medical treatment in case of complaints.
After skin contact
Generally the product does not irritate the skin.
After eye contact
Rinse opened eye for several minutes under running water. If symptoms persist, consult a doctor.
After swallowing
If symptoms persist consult doctor.
Information for doctor
Most important symptoms and effects, both acute and delayed
No further relevant information available.
Indication of any immediate medical attention and special treatment needed
No further relevant information available.


Extinguishing media
Suitable extinguishing agents
Carbon dioxide, extinguishing powder or water spray. Fight larger fires with water spray or alcohol resistant foam.
Special hazards arising from the substance or mixture
If this product is involved in a fire, the following can be released:
Silicon oxide
Advice for firefighters
Protective equipment:
No special measures required.


Personal precautions, protective equipment and emergency procedures
Not required.
Environmental precautions:
Do not allow material to be released to the environment without proper governmental permits.
Do not allow product to reach sewage system or any water course.
Do not allow to penetrate the ground/soil.
Methods and material for containment and cleaning up:
Pick up mechanically.
Prevention of secondary hazards:
No special measures required.
Reference to other sections
See Section 7 for information on safe handling
See Section 8 for information on personal protection equipment.
See Section 13 for disposal information.


Precautions for safe handling
Keep container tightly sealed.
Store in cool, dry place in tightly closed containers.
Information about protection against explosions and fires:
No special measures required.
Conditions for safe storage, including any incompatibilities
Requirements to be met by storerooms and receptacles:
No special requirements.
Information about storage in one common storage facility:
No information known.
Further information about storage conditions:
Keep container tightly sealed.
Store in cool, dry conditions in well sealed containers.
Specific end use(s)
No further relevant information available.


Additional information about design of technical systems:
No further data; see section 7.
Control parameters
Components with limit values that require monitoring at the workplace:
7440-21-3 Silicon (100.0%)
PEL (USA) Long-term value: 15* 5** mg/m³
*total dust **respirable fraction
REL (USA) Long-term value: 10* 5** mg/m³
*total dust **respirable fraction
TLV (USA) TLV withdrawn
EL (Canada) Long-term value: 10 mg/m³
EV (Canada) Long-term value: 10 mg/m³
total dust
Additional information:
No data
Exposure controls
Personal protective equipment
General protective and hygienic measures
The usual precautionary measures for handling chemicals should be followed.
Maintain an ergonomically appropriate working environment.
Breathing equipment:
Not required.
Protection of hands:
Not required.
Penetration time of glove material (in minutes)
Not determined
Eye protection:
Safety glasses
Body protection:
Protective work clothing.


Information on basic physical and chemical properties
General Information
Form: Solid in various forms
Color: Not determined
Odor: Odorless
Odor threshold: Not determined.
pH-value: Not applicable.
Change in condition
Melting point/Melting range: 1423 °C (2593 °F)
Boiling point/Boiling range: 2355 °C (4271 °F)
Sublimation temperature / start: Not determined
Flammability (solid, gaseous)
Not determined.
Ignition temperature: Not determined
Decomposition temperature: Not determined
Auto igniting: Not determined.
Danger of explosion: Not determined.
Explosion limits:
Lower: Not determined
Upper: Not determined
Vapor pressure: Not applicable.
Density at 20 °C (68 °F): 2.33 g/cm³ (19.444 lbs/gal)
Relative density
Not determined.
Vapor density
Not applicable.
Evaporation rate
Not applicable.
Solubility in / Miscibility with Water: Not determined
Partition coefficient (n-octanol/water): Not determined.
dynamic: Not applicable.
kinematic: Not applicable.
Other information
No further relevant information available.


No information known.
Chemical stability
Stable under recommended storage conditions.
Thermal decomposition / conditions to be avoided:
Decomposition will not occur if used and stored according to specifications.
Possibility of hazardous reactions
No dangerous reactions known
Conditions to avoid
No further relevant information available.
Incompatible materials:
Oxidizing agents
No information known.
Hazardous decomposition products:
Silicon oxide


Information on toxicological effects
Acute toxicity:
The Registry of Toxic Effects of Chemical Substances (RTECS) contains acute toxicity data for components in this product.
LD/LC50 values that are relevant for classification:
Oral LD50 3160 mg/kg (rat)
Skin irritation or corrosion:
No irritant effect.
Eye irritation or corrosion:
No irritant effect.
No sensitizing effects known.
Germ cell mutagenicity:
No effects known.
No classification data on carcinogenic properties of this material is available from the EPA, IARC, NTP, OSHA or ACGIH.
Reproductive toxicity:
No effects known.
Specific target organ system toxicity - repeated exposure:
No effects known.
Specific target organ system toxicity - single exposure:
No effects known.
Aspiration hazard:
No effects known.
Subacute to chronic toxicity:
The Registry of Toxic Effects of Chemical Substances (RTECS) contains multiple dose toxicity data for this substance.
Additional toxicological information:
To the best of our knowledge the acute and chronic toxicity of this substance is not fully known.


Aquatic toxicity:
No further relevant information available.
Persistence and degradability
No further relevant information available.
Bioaccumulative potential
No further relevant information available.
Mobility in soil
No further relevant information available.
Additional ecological information:
General notes:
Do not allow material to be released to the environment without proper governmental permits.
Do not allow undiluted product or large quantities to reach ground water, water course or sewage system.
Avoid transfer into the environment.
Results of PBT and vPvB assessment
Not applicable.
Not applicable.
Other adverse effects
No further relevant information available.


Waste treatment methods
Consult state, local or national regulations to ensure proper disposal.
Uncleaned packagings:
Disposal must be made according to official regulations.


Not applicable
UN proper shipping name
Not applicable
Transport hazard class(es)
Not applicable
Packing group
Not applicable
Environmental hazards:
Not applicable.
Special precautions for user
Not applicable.
Transport in bulk according to Annex II of MARPOL73/78 and the IBC Code
Not applicable.
Transport/Additional information:
Marine Pollutant (DOT):


Safety, health and environmental regulations/legislation specific for the substance or mixture
National regulations
All components of this product are listed in the U.S. Environmental Protection Agency Toxic Substances Control Act Chemical substance Inventory.
All components of this product are listed on the Canadian Domestic Substances List (DSL).
SARA Section 313 (specific toxic chemical listings)
Substance is not listed.
California Proposition 65
Prop 65 - Chemicals known to cause cancer
Substance is not listed.
Prop 65 - Developmental toxicity
Substance is not listed.
Prop 65 - Developmental toxicity, female
Substance is not listed.
Prop 65 - Developmental toxicity, male
Substance is not listed.
Information about limitation of use:
For use only by technically qualified individuals.
Other regulations, limitations and prohibitive regulations
Substance of Very High Concern (SVHC) according to the REACH Regulations (EC) No. 1907/2006.
Substance is not listed.
The conditions of restrictions according to Article 67 and Annex XVII of the Regulation (EC) No 1907/2006 (REACH) for the manufacturing, placing on the market and use must be observed.
Substance is not listed.
Annex XIV of the REACH Regulations (requiring Authorisation for use)
Substance is not listed.
REACH - Pre-registered substances
Substance is listed


Safety Data Sheet according to Regulation (EC) No. 1907/2006 (REACH). The above information is believed to be correct but does not purport to be all inclusive and shall be used only as a guide. The information in this document is based on the present state of our knowledge and is applicable to the product with regard to appropriate safety precautions. It does not represent any guarantee of the properties of the product. American Elements shall not be held liable for any damage resulting from handling or from contact with the above product. See reverse side of invoice or packing slip for additional terms and conditions of sale. COPYRIGHT 1997-2016 AMERICAN ELEMENTS. LICENSED GRANTED TO MAKE UNLIMITED PAPER COPIES FOR INTERNAL USE ONLY.

Silicon Isotopes

Silicon has three stable isotopes: 28Si, 29Si and 30Si.

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
22Si 22.03453(22)# 29(2) ms ß+ to 22Al; ß+ to 21Mg 0+ N/A 130.35 -
23Si 23.02552(21)# 42.3(4) ms ß+ to 23Al 3/2+# N/A 146.81 -
24Si 24.011546(21) 140(8) ms ß+ to 24Al; ß+ to 23Mg 0+ N/A 167.93 -
25Si 25.004106(11) 220(3) ms ß+ to 25Al; ß+ to 24Mg 5/2+ N/A 182.53 -
26Si 25.992330(3) 2.234(13) s EC to 26Al 0+ N/A 201.79 -
27Si 26.98670491(16) 4.16(2) s EC to 27Al 5/2+ N/A 215.46 92.2297
28Si 27.9769265325(19) STABLE - 0+ 0 232.85 4.6832
29Si 28.976494700(22) STABLE - 1/2+ -0.55529 240.93 3.0872
30Si 29.97377017(3) STABLE - 0+ 0 251.81 -
31Si 30.97536323(4) 157.3(3) min ß- to 31P 3/2+ N/A 258.02 -
32Si 31.97414808(5) 132(13) y ß- to 32P 0+ N/A 267.03 -
33Si 32.978000(17) 6.18(18) s ß- to 33P (3/2+) N/A 271.38 -
34Si 33.978576(15) 2.77(20) s ß- to 34P 0+ N/A 279.46 -
35Si 34.98458(4) 780(120) ms ß- to 35P; ß- + n to 34P 7/2-# N/A 281.95 -
36Si 35.98660(13) 0.45(6) s ß- to 36P; ß- + n to 35P 0+ N/A 288.17 -
37Si 36.99294(18) 90(60) ms ß- to 37P; ß- + n to 36P (7/2-)# N/A 290.66 -
38Si 37.99563(15) 90# ms [>1 µs] ; ß- + n to 37P; ß- to 38P 0+ N/A 295.94 -
39Si 39.00207(36) 47.5(20) ms ß- to 39P 7/2-# N/A 297.5 -
40Si 40.00587(60) 33.0(10) ms ß- to 40P 0+ N/A 302.78 -
41Si 41.01456(198) 20.0(25) ms ß- to 41P 7/2-# N/A 302.48 -
42Si 42.01979(54)# 13(4) ms ß- to 42P 0+ N/A 305.9 -
43Si 43.02866(75)# 15# ms [>260 ns] Unknown 3/2-# N/A 305.59 -
44Si 44.03526(86)# 10# ms Unknown 0+ N/A 307.15 -