Silicon (Si)

Silicon is a chemical element with the atomic number 14 in the periodic table. With an abundance of 27.7% in Earth’s crust, it’s the second most abundant chemical element. 

Being a member of the carbon family of periodic table elements, this electropositive non-metal element has four valence electrons and numerous naturally occurring compounds. As the temperature increases, silicon’s conductivity improves. This makes element 14 an excellent semiconductor which is an irreplaceable part of modern electronic devices. 

Fact Box

Chemical and Physical Properties of Silicon

The symbol in the periodic table of elements: Si

Atomic number: 14

Atomic weight (mass): 28.0855 g.mol-1

Group number: 14

Period: 3 (p-block)

Color: A blue-gray non-metallic substance with a metallic luster

Physical state: Solid at room temperature

Half-life: 

Electronegativity according to Pauling: 1.8

Density: 2.33 g.cm-3 at 20 °C

Melting point: 1414°C, 2577°F, 1687 K

Boiling point: 3265°C, 5909°F, 3538 K

Van der Waals radius: 0.132 nm

Ionic radius: 0.271 (-4) nm ; 0.041(+4)

Isotopes:

Most characteristic isotope: 28Si, 30Si

Electronic shell: [Ne] 3s23p2

The energy of the first ionization: 786.3 kJ.mol-1

The energy of the second ionization: 1576.5 kJ.mol-1

The energy of the third ionization: 3228.3 kJ.mol-1

The energy of the fourth ionization: 4354.4 kJ.mol-1

Discovery date: In 1824 by Jöns Jacob Berzelius

With the periodic table symbol Si, atomic number 14, atomic mass of 28.0855 g.mol-1, and electron configuration [Ne] 3s23p2, silicon is a brittle, hard, solid non-metallic substance with a blue-gray metallic luster. Silicon physically appears as a metal, but it displays strong non-metal properties. Thus, this chemical element is labeled as one of the seven metalloids of the periodic table.

Silicon reaches its boiling point at 3265°C, 5909°F, 3538 K, while the melting point is achieved at 1414°C, 2577°F, 1687 K. This member of the boron family of elements in the periodic table has an electronegativity of 1.8 according to Pauling, whereas the atomic radius according to van der Waals is 0.132 nm. 

The crystalline form of silicon has a diamond structure. There are two allotropes of element 14: a brown amorphous form of silicon and dark crystalline silicon. In compounds, element 14 displays a purely electropositive chemical behavior. 

At room temperature, element 14 is a relatively inactive chemical element. When exposed to high temperatures, this non-metallic substance displays greater chemical reactivity. With this, the conductivity of silicon improves when the temperature increases. Since it’s an uncommon trait for metals, this particular chemical property classifies silicone as a metalloid.                         

How Was Silicon Discovered?

Silicon has been known to the predynastic Egyptians and the ancient Chinese. Natural silicon-based materials and silicon rock crystals have been used by these and other ancient societies mainly for decorative purposes, such as making jewelry beads or vases. They were also using this substance in the mortar for building homes and knew how to make glass out of sand.

The first scientist who had attempted to isolate silicon from rocks was the French chemist and nobleman Antoine Lavoisier (1743-1794). In 1787, this distinguished scientist attempted to reduce an oxide of silicon labeled as silica by using electrolysis, but without much luck. A decade later, Sir Humphry Davy was convinced that the hard, gray substance isolated by Lavoiser contains several other elements, so he labeled it as a compound. 

Another 10 years later, the French chemists Joseph Louis Gay-Lussac and Louis Jacques Thénard took a closer look at Davy’s compound that resembled a meteorite rock. Following Davy’s conclusion, they exposed to heat a mixture of potassium with silicon tetrafluoride, in order to isolate the postulated chemical elements. By this method, Gay-Lussac and Thénard managed to produce only impure amorphous silicon. 

In 1824, the Swedish chemist Jöns Jacob Berzelius (1779 – 1848) became the first among the scientists to discover silicon metal. Namely, Berzelius tried to recreate the experiment of the two French chemists, only this time he heated potassium fluorosilicate and potassium and continued the experiment with purification of the elemental silicon byproducts by using hydrolysis. This chemical maneuver resulted in the production of pure silicon. 

How Did Silicon Get Its Name?

The name silicon is derived from the Latin word ‘silex’ (or ‘silicis’), meaning ‘flint’  (a hard stone, meteorite). 

Where Can You Find Silicon?

In its pure, elemental form, silicon can be found everywhere in the Universe, especially in meteorite rocks. Known since ancient times, silicon is believed to be a cosmic product of alpha-particle absorption. In nature, silicon always occurs in combination with other elements in the Earth’s crust, especially with oxygen. Silicate rocks, for instance, contain both element 14 and oxygen

Silica and silicates are the most abundant form of silicon. The compounds of silicon are also widespread and can be traced in all spheres of the Earth – the atmosphere (as siliceous dust), in all aquatic systems, the biosphere, as well as in the tissues, skeletons, and body fluids of some animals. Plants require silicon for strengthening their cell walls.

In the geosphere, silicon dioxide occurs both in crystalline minerals (quartz, cristobalite, tridymite), in amorphous or seemingly amorphous minerals (agate, opal, chalcedony). This lithophilic element also can be found in clays, feldspar, olivine, pyroxene, amphiboles, micas, zeolites, and ultramarines. 

For commercial purposes, pure silicon is obtained by the reduction of silica (SiO2), silicon tetrachloride, or trichlorosilane with coke in an electric furnace. In the next step, the silicon pieces are grown to form cylindrical single crystals. Then, the impure product undergoes a process of refinement. China, Russia, the United States, and Norway are the world’s leading countries in silicon mining and production. 

Silicon in Everyday Life

Element 14 is one of the most versatile used chemical elements. Its everyday application can be seen in a wide range of industries and branches:

  • Silica sand is one of the most effective filtrators, used in  water filtration for processing well water or filtering the tap water;
  • Silica or silicon dioxide (SiO2) is commonly used for making window glass and drinking glasses;
  • High-purity monocrystalline silicon is used as a semiconductor material, employed as a solar cell to convert radiant energy into electrical energy. In this way, silicon is given an exceptionally significant role in the development of energy. As a semiconductor, silicon is also used in all electronic equipment, like solid-state devices, computer chips, rectifiers, solar panels, transistors, etc. When used in electronic devices, silicon crystals are doped with boron, gallium, germanium, phosphorus, or arsenic for better control of silicon’s electrical properties.
  • Silica (SiO2) (also quartz or quartzite) is used to produce silicon ferroalloys and silicon metal;
  • Silica sand is also used in paints and coatings to improve their durability and dirt-resistance, as well as in the construction and glazing of ceramic products, enamels, flooring, mortars, cement, roofing shingles, asphalt, and other industrial materials;
  • Silicon carbide (SiC) is used as an abrasive due to its hardness that almost equals the one of a diamond;
  • The manufacturing process of today’s modern communication systems and technology greatly depends on pure silica, which is used to draw high transparency glass fiber for optical fiber communication;
  • Silicon is used in manufacturing kitchen utensils, bakeware, cake molds, cups, baby bottles, hot water bottles, etc. Food-grade silicone used in cooking should be made of 100% silicone due to safety reasons;
  • In food, silicon dioxide is used as an anti-clumping agent – it’s what gives an extra crunch to crackers and freshness to cereals;
  • Silicon, oxygen, carbon, and hydrogen are used for manufacturing of silicone – a rubber-like material used for medical implants, lubricants, polishing agents, and electrical insulators;
  • Liquid silicone is used for cosmetic purposes of enhancing facial features or non-surgical correction of the body;
  • Silicon chips are used in quantum computers, which presents a significant milestone in computer technology. Silicon Valley is a region in San Francisco Bay, Northern California, United States, that stands as a global center for high technology and innovation with the main focus on silicon chip production for the computer industries.

How Dangerous Is Silicon?

Silicon does not accumulate in any particular organ or tissue of the body. It’s mainly found in the skin and the connective tissues. 

Despite being classified as a non-toxic substance, prolonged exposure to crystalline silica may lead to silicon toxicity. Crystalline silica exposure typically manifests with lung disease (Silicosis) and chronic obstructive pulmonary disease as common side effects. 

On the other hand, the liquid silicone used for medical purposes or in cosmetic procedures may block blood vessels in the brain, heart, lymph nodes, or lungs. This may further lead to an extremely dangerous and life-threatening condition.

Environmental Effects of Silicon

Most solar cells and solar panels are made with silicon due to its chemical and physical properties. Since solar energy is one of the most environmentally friendly sources of energy. Knowing this, we can freely say that nature has left us a legacy for preserving our environment by giving us silicone in abundance. 

Isotopes of Silicon

There are 23 isotopes of silicon. Their atomic masses range from silicon-22 to silicon-44. With 92.23% occurrence, silicon-28 isotope is the most abundant form of element 14. Almost all isotopes of silicon decay by beta emission to aluminum, phosphorus, or magnesium. 

Nuclide[3]

[n 1]

Z N Isotopic mass (Da)[4]

[n 2][n 3]

Half-life

[n 4]

Decay

mode

[n 5]

Daughter

isotope

[n 6]

Spin and

parity

[n 7][n 4]

Natural abundance (mole fraction)
Excitation energy Normal proportion Range of variation
22Si 14 8 22.03579(54)# 29(2) ms β+ (67.6%) 22Al 0+
β+, p (32.4%) 21Mg
23Si 14 9 23.02544(54)# 42.3(4) ms β+ (12%) 23Al 3/2+#
β+, p (88%) 21Mg
24Si 14 10 24.011535(21) 140(8) ms β+ (62.4%) 24Al 0+
β+, p (37.6%) 23Mg
25Si 14 11 25.004109(11) 220(3) ms β+ (64.8%) 25Al 5/2+
β+, p (35.2%) 24Mg
26Si 14 12 25.9923338(12) 2.2453(7) s β+ 26Al 0+
27Si 14 13 26.98670469(12) 4.15(4) s β+ 27Al 5/2+
28Si 14 14 27.9769265350(5) Stable 0+ 0.92223(19) 0.92205–0.92241
29Si 14 15 28.9764946653(6) Stable 1/2+ 0.04685(8) 0.04678–0.04692
30Si 14 16 29.973770137(23) Stable 0+ 0.03092(11) 0.03082–0.03102
31Si 14 17 30.97536319(5) 157.36(26) min β 31P 3/2+
32Si 14 18 31.9741515(3) 153(19) y β 32P 0+ trace cosmogenic
33Si 14 19 32.9779770(8) 6.18(18) s β 33P (3/2+)
34Si 14 20 33.978575(15) 2.77(20) s β 34P 0+
34mSi 4256.1(4) keV <210 ns IT 34Si (3−)
35Si 14 21 34.98455(4) 780(120) ms β (94.74%) 35P 7/2−#
36Si 14 22 35.98665(8) 450(60) ms β (87.5%) 36P 0+
β, n (12.5%) 35P
37Si 14 23 36.99295(12) 90(60) ms β (83%) 37P (7/2−)#
β, n (17%) 36P
38Si 14 24 37.99552(11) 90# ms [>1 μs] β, n 37P 0+
β 38P
39Si 14 25 39.00249(15) 47.5(20) ms β 39P 7/2−#
40Si 14 26 40.00583(37) 33.0(10) ms β 40P 0+
41Si 14 27 41.01301(60) 20.0(25) ms β 41P 7/2−#
42Si 14 28 42.01768(54)# 12.5(35) ms β 42P 0+
43Si 14 29 43.02480(64)# 15# ms [>260 ns] 3/2−#
44Si 14 30 44.03061(64)# 10# ms 0+

Source: Wikipedia

List of Silicon Compounds 

Silicon compounds have been known to humanity since the Stone Age and are widely distributed in the Earth’s crust. The chemical compounds in which silicon participates are divided into five major industrial groups:

  1. Si–H (hydride functional silanes);
  2. Si–X (halosilanes);
  3. Si–C (organosilanes);
  4. Si–OSi (siloxanes); 
  5. Si–OR (silicon esters).

Silicon adopts the -4, 0, and +4 oxidation states when it participates in a compound. Upon exposure to high temperatures, silicon reacts vigorously with the halogen elements (fluorine, chlorine, bromine, and iodine) to form halides, as well as with certain metals to form silicides. Just like carbon, this chemical element can easily bond to other silicon atoms.

Some of the most commonly occurring or prepared compounds of silicon include:

 

  • Cristobalite
  • Decamethylsilicocene
  • Difluorosilane
  • Gabronite
  • Hyperbranched aminosilica
  • Metasilicic acid
  • Moganite
  • Nickel monosilicide
  • Nitridosilicate
  • Orthosilicic acid
  • Phosphasilene
  • Phosphidosilicates
  • Polysilazane
  • Pyrosilicic acid
  • Silazane
  • Silenes
  • Silicon dioxide
  • Silicon oxynitride
  • Silylone
  • Titanium silicon carbide
  • Tris(tert-butoxy)silanethiol
  • Silicon boride
  • Amorphous silica-alumina
  • Bismuth silicon oxide
  • Calcium silicate
  • Disilene
  • Disiloxane
  • Disilyne
  • Lithium disilicate
  • Lithium metasilicate
  • Polysilicon halides
  • Polysilicon hydride
  • Potassium silicate
  • Reaction bonded silicon carbide
  • Silicon carbide
  • Silicon disulfide
  • Silicon monosulfide
  • Silicon monoxide
  • Silicon nitride
  • Silicon tetraazide
  • Silicon tetrabromide
  • Silicon tetrachloride
  • Silicon tetrafluoride
  • Silicon tetraiodide
  • Silicotungstic acid
  • Silylene
  • Sickle-gloss
  • Silica fume
  • Silica gel
  • Siliceous sponge
  • Sodium metasilicate
  • Sodium silicate
  • Thiosilicate

 

5 Interesting Facts and Explanations

  1. Silicon dioxide (SiO2), also known as silica sand, is a naturally occurring compound composed of two of the earth’s most abundant materials – silicon (Si) and oxygen (O2). It comprises 59% of Earth’s crust. Quartz is the most common form of silica.
  2. Only oxygen is a more abundant element than silicon in Earth’s crust.
  3. In the regular sand (feldspathic sand, brown sand, or construction sand), silica quantity is always less than 95%. 
  4. Quartz is the second most common mineral that naturally occurs on Earth. 
  5. Flint is a form of quartz (nearly pure silica) in a hard grey rocky form which is commonly used with steel to produce an igniting spark (especially in a cigarette lighter).