Silicon

What is Silicon?

Silicon is a metalloid and the 14^th element of the periodic table. It is a hard, brittle, crystalline solid with a blue-grey metallic luster, which is quite different from the rubber-like material, silicone, which is more popularly known. Silicon is used extensively as a semiconductor in the electronics industry, especially computers. It is also one of the main components of sand, quartz, and amethyst.

Silicon’s Place in the Periodic Table

Silicon was named in 1831 by Scottish chemist Thomas Thomson after the Latin word silicis which means flint, which is a form of quartz. Silicon is part of group 14, which is sometimes called the carbon group, named after the first element in the group, carbon. All of the elements in this group, other than germanium, are quite familiar in daily life. Silicon is also one of 6 elements classified as a metalloid, meaning it has properties that are either in between or a mixture of metal and nonmetal properties.

Atomic number: 14
Symbol: Si
Group: 14
Period: 3
Number of Protons: 14
Number of Electrons: 14
Number of Neutrons: 14
Atomic Radius: 111 pm
Atomic mass: 085
Number of Isotopes: 3

Properties of Silicon

Silicon is most commonly a shiny grey element that forms in plates that stack on top of each other. It can be found in its pure form in nature but is also found in countless minerals. It does not corrode easily and is relatively unreactive in standard conditions. Silicon is a semiconductor which means it has conductivity that lies in between that of an insulator and a strong conductor like most transition metals. This is a common property for the metalloid group that silicon belongs to. Silicon is also considered non-toxic to humans and animals.

Physical Properties

Silicon can take on two different physical forms based on whether or not it is in a crystalline structure at the time. The different forms are called allotropes and they represent two different ways silicon atoms can stack and connect to each other. This is mostly due to the pressure conditions the silicon is in. The crystalline structure is more common and forms flat plates of shiny grey, whereas the form with no crystalline structure is a brown powder. Silicon also is relatively light, especially compared to metals, since its density is only about twice that of water.

Melting Point: 1687 K (1414°C)
Boiling Point: 3173 K (2900°C)
Density: 33 g/cm³
Phase at Room Temperature: solid

Chemical Properties

At standard room temperature, silicon doesn’t . However, at higher temperatures silicon can react with acids and is much more likely to dissolve. In its molten form, silicon readily reacts with oxygen, . Silicon definitely prefers to bond; similar to carbon in the way it forms complexes. Carbon and silicon are in the same group and have the same outer shell electron configuration, both having room to form 4 bonds. It is not terribly electronegative but the common +4 oxidation state means it can easily bond to 4 atoms. A lot of very electronegative elements will readily bond with silicon because it has 4 spaces to accept bonds, but it’s low electronegativity itself means it doesn’t attract elements well on its own.

Oxidation states: -4, +4
Specific Heat: 710 J/(kg K)
Electronegativity: 9
Heat of Fusion: 2 kJ/mol
Heat of Vaporization: 359 kJ/mol
Electron Configuration: [Ne]3s²3p²

Isotopes

Silicon has 3 stable, naturally occurring isotopes and about 20 radioisotopes that are much less stable. The naturally occurring isotopes are dominated by ²⁸Si with 92.23% abundance. There is also ²⁹Si with 4.68% abundance and ³⁰Si with 3.09% abundance. The stable isotopes have a couple different uses. For example, ²⁸Si is used for improving thermal conductivity in semiconductors and ²⁹Si is commonly used in NMR spectroscopy, an important chemistry research method.

Alloys and Allotropes

Silicon alloys are very important and prevalent. Silicon can be added to many metals and generally enhances the usual properties of the resulting metal. For example, the alloyed form may make the metal more malleable, or stronger than the pure metal forms. The most common alloy is definitely ferrosilicon which is a combination of silicon and iron. Ferrosilicon is used to deoxidize steal and is a common starting point in the production of many other iron alloys. There are also aluminum-silicon alloys that are known for their ease of casting because of the fluidity of its melted form.

Compounds of Silicon

There are many notable compounds of silicon, but by far the most commonly known is silicon dioxide, or in common words: sand. Most sand you find at the beach or in nature is silicon dioxide with occasional other compounds mixed in. Sand is important for the glass industry, in ceramics, in water filtration systems, and in the manufacturing of paper and rubber. Another common compound is silicon carbide, or carborundum, which is one of the hardest substances known to man. It is commonly used to grind or polish other materials.

Interesting Facts about Silicon

Silicon is the seventh most abundant element in the Universe.
If silicon dioxide, commonly referred to as sand, gets in your lungs, it can cause pneumonia-like symptoms and is called silicosis.
Silicon has a higher density in its liquid form than it does in its solid form.
Many gemstones like quartz and opal have silicon in their chemical structures.
There are certain studies that found plants need silicon to strengthen their cell walls and is an important part of plant nutrition.
Silicon Valley, the tech hub in the Bay Area of California, got its name in 1971 because of the silicon used in computer chips.
Because of its proximity to carbon, the arguable base of human life, many science fiction novels talk about silicon-based life forms.
The Stone Age of history was dominated by sharp flints as tools which were made from minerals with silicon.
The electronics industry requires an incredibly high grade of silicon. It must be 99.9999999% pure which means only one in a billion atoms can be something other than silicon.
The first commercial silicon transistor was announced in 1954.

Occurrence and Abundance of Silicon

Silicon is the second most abundant element in the Earth’s crust (27% abundance), only behind oxygen. In fact, almost every naturally-occurring rock or mineral has some traces of silicon in it. The pure form is most commonly produced from sand, or silicon dioxide. Even though it’s abundant in Earth’s crust, there for silicon. Due to complications like political and commercial incentives, such as environmental protection policies, most countries do not produce as much silicon as you’d expect. China is by far the biggest producer, producing about 4.8 million tons in 2017 compared to the number two producer, Russia, who produced 750 thousand tons. China has several incentives in place to increase consumption of silicon within China and to encourage Chinese tech companies to use Chinese silicon. Silicon can also be found in humans with about 0.026% abundance and in meteorites with about 14% abundance.

Uses of Silicon

Most Notable Uses in General

“Silicon” by JiahuiH is licensed under CC BY 2.0

Chances are, if you have a smartphone or personal computer, it contains a semiconductor or a transistor made of silicon. It is widely used in many electronic devices and can also be found in components like photovoltaic cells, rectifiers, and in parts of computing circuits. It is also a dominant player in the glass industry with almost all glass produced containing silicon dioxide. Silicon is also one of the main components of quartz, which can be ground down to the dust we call sand. Quartz is important for glass and electronics as well, but is most commonly known for its uses as a gemstone which can be featured in jewelry and museums.

Silicon is also one of the main components of silicone, which can take chemical formulas that follow this pattern [R₂SiO]_n. The R is one of many organic functional groups like a methyl (-CH₃) or phenyl (-C₆H₅) group, and the n is the number of compounds in the chemical formula. Silicones are usually heat resistant and can have a liquid or rubber-like consistency. Silicone is used in an abundance of materials such as in sealants, adhesives, cooking utensils, insultation and lubricants. If you’ve ever used a rubber-like oven mitt or cooking spatula, it was probably silicone.

Most Notable Uses in Science

The electronic applications of silicon are obviously just as important for the research world as they are for consumer products, but there are other applications of silicon too. For example, since it is used commonly as an additive to metal alloys, it can improve the strength of steel, help remove impurities, and add resistance to corrosion such as rust. Having so many effects makes silicon an essential ingredient for making equipment for very specific purposes and conditions. For example, many experiments and chemical reactions need equipment that is heat resistant, so silicon products like ceramics and silicone are used. Several silicon alloys are also quite malleable and great for casting to specific shapes, which can be helpful for small, complicated mechanical parts.

Discovery of Silicon

Because silicon is so abundant in the Earth’s crust, ancient and modern civilizations have been using it in tools and building materials for centuries. However, it wasn’t until the 1800s that chemists started trying to extract pure silicon. It was eventually purified and officially discovered by Jons Jacob Berzelius, a Swedish chemist, in 1824.

Silicon in the Future

Because silicon is so vital to the electronics industry, there is always research being done to see how There is even some recent research on silicon for quantum computers, which might someday become the norm. It is also being looked at for the production of incredibly tiny lasers which could potentially transmit data faster than optical cables.