Silicon

Delve into the fascinating world of Silicon, a cornerstone of modern science and technology. This guide illuminates the definition, uses, and significance of Silicon in an educational setting. Tailored for teachers, it offers practical examples and tips to simplify complex concepts, making it easier to impart knowledge to students. Discover how Silicon’s versatile nature shapes our daily lives and the future of technological advancements.

What is Silicon?

Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, crystalline material that is found abundantly in the Earth’s crust. Silicon is renowned for its semiconductor properties, making it essential in the production of electronic devices. In its pure form, it appears as a shiny, grayish metal. Its ability to conduct electricity, particularly when impurities are added, is what makes Silicon so valuable in the tech industry. Silicon is also a key component in the creation of solar panels, playing a crucial role in renewable energy technology. For students and teachers alike, understanding Silicon’s properties and uses is fundamental in the study of both chemistry and physics.

Silicon Element Information

Other Metalloids

Boron (B)

Germanium (Ge)

Arsenic (As)

Antimony (Sb)

Tellurium (Te)

Silicon Formula

• Formula: Si
• Composition: A single silicon atom.
• Bond Type: Silicon forms strong covalent bonds, thanks to its four valence electrons.
• Molecular Structure: Solid at room temperature, displaying a crystalline structure.
• Electron Configuration: 14 electrons, with the configuration 1s² 2s² 2p⁶ 3s² 3p².
• Significance: Integral in electronics as a semiconductor material, used in solar cells, and in making glass and building materials.
• Role in Chemistry: Silicon is pivotal in the development of new materials, playing a significant role in polymer chemistry and nanotechnology.

Atomic Structure of Silicon

Properties of Silicon

Physical Properties of Silicon

Property	Description
Appearance	Shiny, metallic grey in color
Density	2.33 g/cm³
Melting Point	1414 °C
Boiling Point	3265 °C
Crystal Structure	Diamond cubic
Electrical Conductivity	Semiconductor
Thermal Conductivity	149 W/(m·K) at 25 °C
Hardness	Relatively hard, brittle

Chemical Properties of Silicon

Silicon, a metalloid, exhibits a mix of metallic and non-metallic properties. Its atomic number is 14 and it’s situated in group 14 of the periodic table.

1. Reaction with Oxygen: Silicon reacts with oxygen to form silicon dioxide (SiO₂): Si(s)+O₂​(g)→SiO₂​(s) Silicon dioxide forms the basis of most minerals on Earth.
2. Reaction with Halogens: It reacts with halogens at high temperatures, forming tetrahalides like silicon tetrachloride (SiCl₄): Si(s)+2Cl₂​(g)→SiCl₄​(l)
3. Reaction with Water: Silicon doesn’t react with water under normal conditions, contributing to its stability and wide use in technology and construction.
4. Formation of Silicones: When reacted with organic compounds, silicon forms silicones, versatile polymers used in a myriad of applications.
5. Role in Semiconductors: In its crystalline form, silicon’s semiconductor properties are utilized in electronics and photovoltaic cells. Its ability to conduct electricity increases with temperature, and it can be doped with other elements like phosphorus or boron to enhance its conductivity.
6. Allotropes: Silicon exists in two allotropic forms; amorphous silicon, used in solar cells, and crystalline silicon, used in electronic devices.
7. Silicon-Hydrogen Compounds: Silicon forms hydrides known as silanes (SiₓHₓ₊₂). Silanes decompose in the presence of oxygen, burning and forming silicon dioxide.
8. Behavior with Metals and Nonmetals: Silicon forms various compounds with metals (silicides) and nonmetals. It’s less reactive compared to carbon, the other group 14 element, and forms more stable compounds with larger atoms.

Thermodynamic Properties of Silicon

Property	Value with Unit
Boiling Point	3265 °C
Melting Point	1414 °C
Heat of Vaporization	384 kJ/mol
Heat of Fusion	50.21 kJ/mol
Specific Heat Capacity (at 25°C)	19.789 J/mol·K
Thermal Conductivity	149 W/m·K

Material Properties of Silicon

Property	Value with Unit
Density (at 25°C)	2.3290 g/cm³
Viscosity	NA (Solid at room temperature)
Solubility in Water	Insoluble
Refractive Index	3.42 (at 590 nm)
Surface Tension	NA (Solid at room temperature)
Mohs Hardness	7
Elastic Modulus	130-188 GPa
Poisson’s Ratio	0.064-0.28

Electromagnetic Properties of Silicon

Property	Value with Unit
Electrical Resistivity (at 20°C)	2.3 × 10^3 Ω·m
Thermal Conductivity	149 W/m·K
Band Gap	1.12 eV at 300K
Dielectric Constant	~11.68 at 1MHz
Magnetic Susceptibility	-4.2 × 10^-6 cm^3/mol
Electronegativity (Pauling scale)	1.90

Nuclear Properties of Silicon

Property	Value with Unit
Atomic Number	14
Atomic Mass	28.085 amu
Isotopes	^28Si (92.23%), ^29Si (4.67%), ^30Si (3.1%)
Nuclear Spin (for ^28Si)	0 ℏ (Zero spin for most abundant isotope)
Neutron Cross Section (for ^28Si)	2.33 barns
Nuclear Magnetic Moment (for ^29Si)	-0.55529 µN

Chemical Compounds of Silicon

Silicon forms a variety of compounds, many of which are integral to industries ranging from electronics to construction. Here are six significant silicon compounds along with their relevant chemical equations:

1. Silicon Dioxide (SiO₂)
   Equation: Si+O₂​→SiO₂​
   Silicon dioxide, also known as silica, is found in quartz and is a major component of sand.
2. Silicon Carbide (SiC)
   Equation: $\text{Si}+\text{C}\to \text{SiC}$
   Known for its hardness, it’s used as an abrasive and in cutting tools.
3. Silicon Tetrachloride (SiCl₄)
   Equation: Si+2Cl₂​→SiCl₄​
   Used in producing high purity silicon and silica for commercial applications.
4. Silanes (SiH₄)
   Equation: Si+2H₂​→SiH₄​
   Silanes are used in semiconductor industry and as a reducing agent.
5. Silicon Nitride (Si₃N₄)
   Equation: 3Si+2N₂​→Si₃​N₄​
   Known for its high strength and resistance to heat, used in ceramics and engine parts.
6. Ferrosilicon (FeSi)
   Equation: $\text{Fe}+\text{Si}\to \text{FeSi}$
   An alloy of iron and silicon, used in steelmaking as a source of silicon.

Isotopes of Silicon

Isotope	Abundance	Properties
Silicon-28 (²⁸Si)	92.23%	Most abundant isotope, stable
Silicon-29 (²⁹Si)	4.67%	Stable, used in NMR spectroscopy
Silicon-30 (³⁰Si)	3.10%	Stable, minor natural abundance
Silicon-31 (³¹Si)	Trace	Radioactive, half-life of 157.3 minutes
Silicon-32 (³²Si)	Trace	Radioactive, used in oceanographic studies
Silicon-34 (³⁴Si)	Synthetic	Radioactive, used for research purposes

The isotopes of silicon vary in their abundance and stability, with Silicon-28 being the most common. Radioactive isotopes like Silicon-31 and Silicon-32 have specialized uses in scientific research.

Uses of Silicon

Silicon, a versatile element, has numerous applications across various industries. Here are the top five uses of silicon:

1. Electronics and Computing

Silicon is a primary component in semiconductors, making it fundamental to the manufacturing of microchips, transistors, and other electronic components used in computers, smartphones, and numerous other digital devices.

2. Solar Energy

Silicon is used in the production of solar cells and panels. Its ability to convert sunlight into electricity efficiently makes it ideal for renewable energy technologies.

3. Alloys

Silicon is used to make various alloys, such as aluminum-silicon and ferrosilicon, which are essential in automotive and aerospace industries for manufacturing engine blocks, machine parts, and more.

4. Construction Materials

Silicon is a key ingredient in producing glass, concrete, and cement. Silica, in the form of sand, is used in construction to make concrete and mortar.

5. Silicone Products

Silicone, made from silicon, oxygen, carbon, and hydrogen, is used in a wide range of products like lubricants, adhesives, sealants, medical devices, and cookware due to its durability and flexibility.

Commercial Production of Silicon

The commercial production of silicon primarily involves the reduction of silica (SiO₂) to produce metallurgical grade silicon. The process is as follows:

1. Raw Material Preparation: Silica, in the form of quartz, is combined with carbon materials like coal, coke, or wood chips. These raw materials are then finely ground and mixed.
2. Reduction in Electric Arc Furnaces: The mixture is placed in an electric arc furnace, where it is heated to temperatures above 1900°C. In this high-temperature environment, the carbon reacts with the oxygen in the silica, reducing it to silicon. The reaction can be represented as: SiO2+2C→Si+2COSiO2​+2C→Si+2CO.
3. Purification and Refining: The resultant metallurgical grade silicon contains impurities like iron, aluminum, and calcium. It undergoes further refining processes, including slag treatment, directional solidification, and acid leaching, to remove these impurities.
4. Conversion to Polysilicon: For electronics and solar cell applications, metallurgical grade silicon is further purified to produce polysilicon, a highly pure form of silicon. This is achieved through a process called the Siemens process, where the silicon is converted into a gas (trichlorosilane) and then reduced back to silicon with hydrogen at high temperatures.
5. Final Product: The final product is either metallurgical grade silicon for aluminum alloys and the chemical industry or polysilicon for the electronics and solar industry.

Health Effects of Silicon

The health effects of silicon largely depend on its form and how it is used or encountered:

1. Inhalation: Prolonged inhalation of fine silica dust, primarily in industrial settings, can lead to silicosis, a serious lung disease. This condition is marked by inflammation and scarring in the lungs and can be debilitating or even fatal.
2. Silica in Food and Pharmaceuticals: Silicon, in the form of silica or silicon dioxide, is often used as an anti-caking agent in foods and pharmaceuticals. In these forms, it’s generally recognized as safe by health authorities. The body doesn’t absorb silicon dioxide, and it’s excreted unchanged.
3. Silicon Supplements: Silicon is also available in dietary supplements, often promoted for bone and connective tissue health. The body requires silicon for the growth and development of bones, but the necessity and effectiveness of supplements remain under investigation.
4. Skin Contact: While elemental silicon poses little to no risk on skin contact, certain silicon compounds used in industrial settings can cause skin irritation or dermatitis upon prolonged exposure.
5. Silicon in Medical Devices: Medical grade silicone, used in implants and medical devices, is biocompatible and generally safe, but there can be risks of allergic reactions or complications in some individuals.

Environmental Effects of Silicon

Silicon’s environmental effects are relatively mild compared to many other elements, primarily because it naturally occurs in abundance in the environment:

1. Abundance in Earth’s Crust: Silicon is the second most abundant element in the Earth’s crust. It is a major component of rocks, sands, and clays, and thus, it is widely distributed in the natural environment.
2. Silica Dust: The primary environmental concern related to silicon is the generation of silica dust from industrial activities like mining, quarrying, and stone cutting. This dust can contribute to air pollution and respiratory problems in humans and animals in the vicinity.
3. Water Pollution: Industrial processes that use silicon compounds can lead to water pollution if waste products are not properly managed. Silicon itself, however, does not dissolve easily in water and is generally not considered a major water pollutant.
4. Impact on Plants: Silicon is beneficial for plant growth. It is taken up by plants and can improve their resistance to disease and stress. In agriculture, silicon is sometimes added to soil to enhance crop growth.
5. Silicon-Based Materials: While elemental silicon and most silicon compounds have minimal environmental impact, certain silicon-based polymers and materials, like silicones, can be persistent in the environment. Their breakdown and disposal require careful management to minimize environmental impact.

What is Silicon Used For?

Silicon is primarily used in electronics as a semiconductor, in solar panels, and as a component in various alloys and silicones.

Is Silicon a Metal or a Plastic?

Silicon is a metalloid, possessing properties of both metals and non-metals, and is not classified as a plastic.

What is Silicon vs Silicone?

Silicon is a natural chemical element, while silicone is a synthetic polymer made from silicon, oxygen, carbon, and hydrogen.

Where is Silicon Found on Earth?

Silicon is abundantly found in the Earth’s crust, primarily as a component of silica and silicate minerals.

Silicon stands as a cornerstone in modern technology and construction. Its versatility in electronics, solar energy, and as a building material underscores its importance. Embracing its potential while understanding its limitations is key to innovating sustainably and efficiently.