Silicon: Occurrence, Properties, Allotropes, Uses and Isotopes

  • Silicon, the second most abundant element after Oxygen on Earth is an essential daily life element.
  • Silicon is a member of the carbon family in group IV A.
  • Silicon has 14 electrons.
  • Its atomic number is 14 whereas its atomic mass is 28.
Naming and History

The name Silicon is derived from the Latin word “silex” which means “flint”.

Silicon as flint was known to humans from the stone age. Tools made from flint were used in everyday life. French chemist Antoine Lavoisier in 1789, suggested that there is a new element in quartz which is also very abundant on Earth.

The abundance of new elements arouses curiosity in chemists. Initially attempts to obtain silicon from electrolysis failed. History reveals that sir Humphry Davy in 1808, attempted to partly isolate silicon and suggested the name silicium.

Two French chemists, Joseph Lussac and Louis Jacques in 1811, produced an impure form of silicon by reacting silicon tetrachloride with potassium. The real credit for silicon discovery goes to Swedish Chemist Jacob Berzelius. In 1824. Berzelius obtained silicon by heating potassium fluorosilicate chips in a silica container.

The product obtained was impure due to the contamination of potassium. He washed the residue with water, with which it reacts and pure silica powder was obtained.


Occurrence of Silicon

Silicon is the second most abundant element making 25 – 28% of Earth’s crust. It is very essential and abundant in the mineral world. Though not present in pure form but exists as compounds with oxygen and other elements.


The most common is silica which occurs as sand, beach dirt, quartz, flint, and in purest forms occurs as gems which are opal, agates, jasper.  Other important rocks and minerals which include silicon are clay, asbestos, mica, granite, talc, etc.

Properties of Silicon

Silicon is a shiny, grey, very brittle, tetravalent, and sometimes bivalent crystalline metalloid. It is electropositive and shares characteristics with other metals. As it is tetravalent like carbon, it forms halides, various oxides, and hydrides.

Silicon is solid at room temperature. The melting point of silicon is 1414°C and the boiling point is 3265°C. The density of silicon is 2.3296 grams per cubic centimeter. Silicon, like water, expands on freezing.

Silicon in Biological Systems

Silicon is essential for plants. Some plants form tiny particles of silicon called phytoliths. They do not rot and remain in fossils help in the dating and provide evolutionary evidence. Diatoms form their cell walls with silica which they extract from the water.

In humans, long-term exposure to silicon such as in miners and stone cutters can cause a severe lung disease called silicosis.

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Silicon as Semi-conductor

Semiconductors are materials that have conductivity between conductors and insulators. They give useful properties and are used to manipulate, rectify, amplify and witch electrical current.

Silicon as the semi-conductor is an integral part and forms the basis of modern electronics. Silicon is used to power integrated circuits of computers, microwaves, and other electronics. Silicon chips are used in processors and circuits of computers.

In microelectronic devices, silicon wafers are used as substrates. Silicon is also part of televisions, cameras, IC cards, and smartphones.

Silicon is widely used as a semiconductor due to its useful properties and abundance.

Allotropes of Silicon

There are two allotropes of silicon at room temperature.

Amorphous Silicon

Amorphous silicon is a brown powdery substance. In this, all atoms are not bonded to their maximum but are connected. This one is great in use for solar cells in toys, watches, calculators, and even solar panels.

Crystalline Silicon

Crystalline silicon or polycrystalline is lustrous, grayish, metallic solid substance. These crystals can be made by a process called the Czochralski process. These crystals in combination with other elements like boron, germanium, phosphorus are used in electronic chips, rectifiers, transistors, solar cells of electronic devices.

Uses of Silicon

The basic and modern use of silicon is as a semiconductor in making microchips, transistors, rectifiers, amplifiers, and other things for electronic devices.

  • Silicon has significant importance in the steel industry.
  • Silicon is the major constituent of the glass, ceramic, cement, and electronics industry.
  • Silicon is a refractory material used in making enamel and pottery.
  • Silicon glasses are formed from melted quartz sand; these glasses are widely used in laboratories, chemical plants, and insulators.
  • Silicon carbide is used as an abrasive.
  • Sodium silicate also called water glass has a wide range of use in soaps and adhesive production and preservation of eggs.
  • Silicon is an important part of silicone, a material used in making medical implants, baking dishes, kitchenware, cooking objects, etc.


Isotopes of Silicon

Silicon has 14 isotopes ranging from mass number 22 to 36. Silicon has three naturally occurring stable isotopes: 28- Silicon, 29- Silicon, and 30- Silicon. Around 92% of silicon is 28- Silicon.

MCQs about Silicon

  • Which Latin word does the name “Silicon” originate from?
    • A) Silicate
    • B) Silex
    • C) Silica
    • D) Siliconium
    • Answer: B) Silex
  • Who is credited with the discovery of silicon?
    • A) Antoine Lavoisier
    • B) Sir Humphry Davy
    • C) Joseph Lussac
    • D) Jacob Berzelius
    • Answer: D) Jacob Berzelius
  • What is the most abundant compound of silicon found in nature?
    • A) Silicate
    • B) Silicon dioxide
    • C) Silicon carbide
    • D) Silicon tetrafluoride
    • Answer: B) Silicon dioxide
  • What is the melting point of silicon?
    • A) 1414°C
    • B) 1000°C
    • C) 3265°C
    • D) 0°C
    • Answer: A) 1414°C
  • What is the main form in which silicon is found in plants?
    • A) Silicon dioxide
    • B) Silica gel
    • C) Phytoliths
    • D) Silicon hydride
    • Answer: C) Phytoliths
  • Which disease is associated with long-term exposure to silicon in humans?
    • A) Diabetes
    • B) Arthritis
    • C) Silicosis
    • D) Pneumonia
    • Answer: C) Silicosis
  • What is the primary use of silicon in the electronics industry?
    • A) Insulator
    • B) Conductor
    • C) Semiconductor
    • D) Superconductor
    • Answer: C) Semiconductor
  • Which process is used to produce crystalline silicon?
    • A) Electrolysis
    • B) Czochralski process
    • C) Distillation
    • D) Polymerization
    • Answer: B) Czochralski process
  • What is the major constituent of silicon carbide?
    • A) Silicon dioxide
    • B) Silicon monoxide
    • C) Silicon tetrafluoride
    • D) Silicon hydride
    • Answer: A) Silicon dioxide
  • What is the most common use of silicon carbide?
    • A) Insulator
    • B) Refractory material
    • C) Semiconductor
    • D) Lubricant
    • Answer: B) Refractory material
  • Which is the most abundant stable isotope of silicon?
    • A) 28-Silicon
    • B) 29-Silicon
    • C) 30-Silicon
    • D) 32-Silicon
    • Answer: A) 28-Silicon
  • What percentage of silicon is naturally occurring stable isotope 28-Silicon?
    • A) 68%
    • B) 78%
    • C) 92%
    • D) 100%
    • Answer: C) 92%
  • What is the main form of silicon used in solar cells?
    • A) Amorphous silicon
    • B) Crystalline silicon
    • C) Silicon dioxide
    • D) Silicon carbide
    • Answer: A) Amorphous silicon
  • Which substance is formed from melted quartz sand and widely used in laboratories and chemical plants?
    • A) Silicon carbide
    • B) Silicon dioxide
    • C) Silicon nitride
    • D) Silicon glass
    • Answer: D) Silicon glass
  • What material is silicon commonly used to make in the medical field?
    • A) Titanium
    • B) Silicone
    • C) Carbon fiber
    • D) Nylon
    • Answer: B) Silicone
  • Which element is commonly added to silicon to produce electronic chips?
    • A) Boron
    • B) Oxygen
    • C) Nitrogen
    • D) Fluorine
    • Answer: A) Boron
  • What is the main property of silicon that makes it suitable for use in integrated circuits?
    • A) High electrical conductivity
    • B) Low melting point
    • C) High melting point
    • D) Variable valency
    • Answer: C) High melting point
  • What is the color of amorphous silicon?
    • A) Grayish
    • B) Brown
    • C) Metallic
    • D) Transparent
    • Answer: B) Brown
  • Which substance is not commonly made using silicon?
    • A) Steel
    • B) Glass
    • C) Cement
    • D) Aluminum
    • Answer: D) Aluminum
  • Which type of silicon is used in solar panels?
    • A) Amorphous silicon
    • B) Crystalline silicon
    • C) Silicon carbide
    • D) Silicon nitride
    • Answer: B) Crystalline silicon
  • What is the common use of sodium silicate?
    • A) Food preservative
    • B) Adhesive
    • C) Cooking oil
    • D) Cleaning agent
    • Answer: B) Adhesive
  • Which form of silicon is used as an abrasive?
    • A) Silicon carbide
    • B) Amorphous silicon
    • C) Silicon dioxide
    • D) Silicon monoxide
    • Answer: A) Silicon carbide
  • Which process is commonly used to obtain silicon from silicon tetrachloride?
    • A) Electrolysis
    • B) Oxidation
    • C) Reduction
    • D) Hydrolysis
    • Answer: C) Reduction
  • What is the group number of silicon in the periodic table?
    • A) Group II
    • B) Group III
    • C) Group IV
    • D) Group V
    • Answer: C) Group IV
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Silicon, the second most abundant element on Earth after Oxygen, plays a crucial role in various aspects of daily life. Derived from the Latin word “silex,” meaning “flint,” silicon’s history traces back to ancient times when it was recognized as flint. Despite initial challenges in isolation, Swedish Chemist Jacob Berzelius successfully obtained pure silicon in 1824, marking a significant milestone in its discovery.

Comprising 25-28% of the Earth’s crust, silicon primarily exists in compound forms, notably as silica. Its properties include being a shiny, grey, tetravalent metalloid with a high melting point of 1414°C and a boiling point of 3265°C. Notably, silicon’s role extends beyond the inorganic realm, as it is essential for plant growth and is utilized in various biological systems.

One of silicon’s most significant applications lies in its use as a semiconductor, forming the backbone of modern electronics. It powers integrated circuits in computers, microwaves, and smartphones, among other devices. Silicon’s allotropes, including amorphous and crystalline forms, serve diverse purposes ranging from solar cell production to electronic chip manufacturing.

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Moreover, silicon finds extensive use in industries such as steel production, glass manufacturing, ceramics, and refractories. Its isotopes, with stable variants like 28-Silicon, contribute to various scientific and industrial applications.

In essence, silicon’s abundance, versatile properties, and wide-ranging applications underscore its indispensable role in modern civilization.