What Type Of Element Is Silicon? Properties & Compounds Of Silicon

Silicon is the fourteenth element of the periodic table. It is a unique element. In this article, you will get to know what type of element silicon is and why it is unique.

Silicon forms different compounds with over 60 stable elements in existence. Silicon does not readily form ions because of its tetravalent nature. It requires a lot of energy to remove or gain more electrons.

Just like carbon, it rather gets into covalent bonding where it shares electrons with a nonmetal. Silicon is not one of the very reactive elements but there is so much to learn about it.

What type of element is silicon?

Your first guess may be a metal but it is not. Silicon is a metalloid. That is, it has both metallic and nonmetallic properties among its physical and chemical properties.

Silicon is the second most abundant element on the Earth’s crust. It takes up 28% of the Earth. However, it does not exist in its free form. Silicon is sourced from silicate which makes up rocks.

The word “silicon” comes from the Latin word “silex or silicus” which means “hard” or “flint” stone. Impure silicon was readily available but in 1824, a Swedish chemist, Jöns Jacob Berzelius, extracted pure silicon.

But, this silicon was in its amorphous form until 1854 when crystalline silicon was produced through electrolysis.

What are the physical properties of silicon?

  • Silicon is a hard and brittle crystalline solid with a blue-grey metallic luster
  • It is located in the p-block, in group 14, period 3 of the periodic table
  • Silicon has an atomic number of 14 and an atomic weight of 28.085
  • It is a solid at STP with a melting point of 2,577°F (1,414°C) and a boiling point of 5,909°F (3,265°C). The high melting and boiling points of this element are due to the strong covalent bonds within its large structure, just like carbon
  • Silicon has four electrons in its outermost shell; a tetravalent atom
  • Furthermore, it has a density of 2.57 g/cm3 at its melting point. Near room temperature, its density drops to 2.3290 g/cm3
  • It takes 50.21 kJ/mol (heat of fusion) to convert one mole of solid silicon to liquid and 383 kJ/mol (heat of vaporization) to convert the liquid into a gas
  • The first, second, and third ionization energies of silicon are as follows: 786.5 kJ/mol, 1,577.1 kJ/mol, and 3,231.6 kJ/mol respectively
  • In addition, silicon has an electronic configuration of [Ne] 3s23p2 with 2, 8 & 4 electrons in its shells
  • In most compounds, silicon is in its +4 oxidation state. However, it can exhibit oxidation states within -4 to +4

What are the chemical properties of silicon?

  • Silicon has similar chemical  characteristics to metals
  • Silicon forms different compounds with a lot of elements. However, it is not very reactive at room temperature. Silicon readily combines with elements at high temperatures
  • Molten silicon readily forms alloys
  • Also, silicon is a very electropositive element

Uses of silicon

  • Silicon is used to make materials such as ceramics, bricks, cement, and silicone
  • As a good semiconductor, it is useful in the making of transistors
  • Silicon is also used in computer processors and solar cells
  • Items made with silicone are usually water-, heat-, moisture-, and oxidation-resistant which makes them durable and useful for the manufacture of waterproof materials, kids’ eating bowls and spoons, etc
  • Silicon is a component of an alloy, ferrosilicon

Some silicon compounds

Silicon dioxide

Silicon dioxide (SiO2) is commonly called silica. It is a linear molecule made of one silicon atom and two oxygen atoms. It exists in crystalline forms such as quartz, cristobalite, and tridymite.

There are two types of silica, namely: colloidal and reactive silica. Colloidal silica is a polymeric form of silica while reactive silica is the monomeric form. As their names imply, colloidal silica is the nonreactive silica.

Furthermore, silica has a high melting point and boiling point. The values stand at approximately 2,912°F (1,600°C) and  4,046°F (2,230°C), respectively. Both forms of silica are naturally amorphous but insoluble in water. They are also nonvolatile and poor conductors of electricity.

Silica finds lots of applications across different industries. It is a common drying agent used in laboratories and other industries. Quartz is a piezoelectric material with applications in radio and television broadcasting and mobile communications.

Additionally, the high melting point of silica makes it perfect for iron and modern sand casting. It also finds applications in filtering plants and hydraulic fracturing of tight oil.


Silicones are often mistaken for silicon. The former is a compound of silicon, while the latter is an element. Silicones are polymers of R2SiO units, where R is an alkyl or aryl group).

Materials made with silicone are water-resistant. They also show high thermal stability, which is why silicone is used in the making of semiconductors, insulators, gaskets, sealants, and waterproof materials.

In addition, silicone is oxidation, chemical, and moisture-resistant. It is also very durable and eco-friendly. They are also useful in surgical and cosmetic surgeries.


Silicates are made of units of SiO4. The units share links via the oxygen atoms to form chains, rings, sheets, or 3-D structures. Chains, rings, and sheets do not have all four corners of the tetrahedral SiO4 linked.

The SiO4 units form a solid, well-defined 3-D structure when all four corners of each discrete unit are linked to other units. Silicate crystals readily form solid hydrates. They are useful in the production of cement, ceramics, and glass.


Zeolites are hydrated aluminosilicate minerals. They are an interlinked tetrahedra network of alumina (AlO4) and silica (SiO4). They are very porous crystalline solids with a 3-D structure.

Besides aluminum, oxygen, and silicon, these minerals contain alkali and alkaline-earth metals such as magnesium, sodium, and potassium. Pure zeolites are rare. Most naturally occurring zeolites contain other minerals, metals, and quartz.

Zeolites are large compounds with a large surface area. They are non-corrosive and have high hydrothermal stability.

Zeolites are useful catalysts for cracking hydrocarbons in petrochemical industries. These industries find them useful because they do not have adverse effects on the environment.

What is the effective nuclear charge of silicon?

Silicon has an electronic configuration of 1s22s22p63s23p2. The effective nuclear charge, Zeff, of an electron is a difference between the nuclear charge of the atom and the shielding constant of the electron of concern.

Zeff = Z – S. Z is the nuclear charge (or atomic number)

Silicon has three shells: the inner shell, the (n-1) shell, and the nth shell.

The electrons in the inner shell are present in the 1s orbital, the (n-1) shell electrons are present in the 2s and 2p orbitals, and the electrons in the nth shell are present in the 3s and 3p orbitals.

The 1s orbital has 2 electrons, the 2s, and 2p orbitals have 8 electrons, and the 3s and 3p orbitals have 3 electrons. The 1s orbital experiences a shielding effect of 1, the 2s and 3p orbitals experience a shielding effect of 0.85, and the 3s and 3p orbitals experience a shielding effect of 0.35.

The shielding constant can be determined as follows:

S = (0.35 x 3) + (0.85 x 8) + (1 x 2)

S = 9.85

Zeff = 14 – 9.85

Zeff = 4.15


What is the molecular geometry of silicon?

Silicon is a tetravalent atom. It has a tetrahedral molecular geometry with a Si-I bond of 2.432 Å.

What is the hybridization of silicon in silica?

In silica, silicon has an sp3 hybridization. In this compound, silicon shares four sigma bonds with the four oxygen atoms.

How many isotopes of silicon are there?

There are three stable isotopes of silicon: silicon-28, silicon-29, and silicon-30. Silicon-28 is the most abundant silicon. It makes up 92.21% of the silicon present in the Earth. Silicon-29 and silicon-30 make up 4.70% and 3.09%, respectively.

There are also radioactive isotopes of silicon: silicon-31, silicon-32, and silicon-33.


Silicon is a unique type of element. Apart from its tetravalent nature, it has more unique characteristics. One of them is its ability to form compounds with over 60% of the stable elements of the periodic table.

Also, it can act as a conductor and an insulator. This is one of the reasons why it has application in electricity. Silicon can be used to make semiconductors and insulators.

Other uses include the production of silicone, a good material for making kids’ bowls. Silicone is a better alternative to plastic and glass.

Silicon shares some similarities with carbon but is not as reactive as carbon because of its tetravalent nature. Although silicon would rather not, it can form ions.

Learn more about the charge of silicon.

Thanks for reading.