Silicon Dioxide

Introduction

Imagine walking on a beach. Fine grains of sand lie underneath your feet. That sand is composed chiefly of silicon dioxide, SiO₂—such an inorganic compound features very importantly in our daily lives and almost in all scientific applications. While Silicon dioxide is not found as an independent natural material, it is literally the heart content in many industrial applications preferably for making glass and ending at electronics. Many people generally term it silica. As such, it is amazingly ubiquitous and will be capable of providing frameworks for thousands of both natural and synthetic products in modern times. It defines its elasticity in terms of properties, hence applicable to an extremely wide variety of materials—from everyday use to cutting-edge technologies. Hardness, chemical inertness, and thermal stability will help to explain in the process the nature of silicon dioxide, its forms, types, and their meanings during everyday life and advanced technology applications.

Key Concept: Definition and Explanation ▹

It is a chemical compound with an empirical formula featuring one silicon atom bonded to two oxygen atoms. Otherwise, it is simply called silica. It is one of the most abundant materials available on Earth in quartz, sand, and even in living organisms. Basically, silicon dioxide represents the hard compound that provides complete chemical inertness. Due to such stability, it remains essentially imperative for geological formation and provides wide applications in several industrial processes.

95% of the earth’s crust is made up of silica and silicates. Silicon dioxide, commonly known as silica, occurs in several crystallographic forms. Quartz, cristobalite, and tridymite are some of the crystalline forms of silica, and they are interconvertible at suitable temperatures. Silicon dioxide is a covalent, three-dimensional network solid in which each silicon atom is covalently bonded in a tetrahedral manner to four oxygen atoms. Each oxygen atom in turn covalently bonded to other silicon atoms as shown in the figure. Each corner is shared with another tetrahedron. The entire crystal may be considered as a giant molecule in which eight-membered rings are formed with alternate silicon and oxygen atoms.

Silica in its normal form is almost non-reactive because of very high Si—O bond enthalpy. It resists the attack by halogens, dihydrogen, and most of the acids and metals even at elevated temperatures. However, it is attacked by HF and NaOH.

$\begin{aligned} & \mathrm{SiO}_2+2 \mathrm{NaOH} \rightarrow \mathrm{Na}_2 \mathrm{SiO}_3+\mathrm{H}_2 \mathrm{O} \\ & \mathrm{SiO}_2+4 \mathrm{HF} \rightarrow \mathrm{SiF}_4+2 \mathrm{H}_2 \mathrm{O}\end{aligned}$

Quartz is extensively used as a piezoelectric material; it has made it possible to develop extremely accurate clocks, modern radio and television broadcasting, and mobile radio communications. Silica gel is used as a drying agent and as a support for chromatographic materials and catalysts. Kieselghur, an amorphous form of silica is used in filtration plants.

Different Aspects and Types of Silicon Dioxide

It can take forms that may well pluralize their properties and uses. Their common ones are crystalline and amorphous silica. The atomic structure of silica, as in quartz, and crystalline, gives it extraordinary strength and is the basic raw material used for making glass, ceramics, and cement. While crystalline silica exhibits an ordered atomic structure, amorphous silica does not; hence its properties differ substantially. That includes other uses that extend into applications such as a flow agent in pharmaceuticals and food products. Also, most synthetic forms of silica, such as fumed silica, find an application in rubber reinforcing and other applications like coatings and adhesives due to the fine particulate nature of such synthetic forms of silica.

Relevance and Applications in Real Life and Academics

Silicon dioxide relates to more than just the beach or that piece of quartz. Silica, in everyday life, could be used in making glass; that is something applied extensively to windows on which we gaze out at life, bottles that drink from, and screens displayed to our faces. Besides, it has high thermal and chemical stability, so it is one of the central requirements in the current high-temperature industrial processes for the manufacture of wafers used in electronics. Material scientists and chemists do extended research in the academically useful silicon dioxide in search of new unique properties that can enable them to come up with advanced materials and technologies. This is utilized in providing insulation or for making protective layers for some parts of the major components in computers and other smartphones. Some of the applications include semiconductor devices. It is also resorted to in the medical field owing to its being biocompatible: in implant materials, particularly in drug delivery systems.

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Some Solved Examples

Example 1
Question:
Silica in its normal form is almost non-reactive because of:
1) Very low Si-O bond enthalpy
2) Very high Si-O bond enthalpy
3) Oxide layer formation on its surface
4) It is a non-metallic compound

Solution:
Silica (SiO₂) has a network structure. It is almost inert because of the very high bond enthalpy of the Si-O bond.

Hence, the correct answer is Option (2).

Example 2
Question:
The amorphous form of silica is:
1) Tridymite
2) Kieselguhr
3) Cristobalite
4) Quartz

Solution:
Quartz, Tridymite, and Cristobalite are crystalline forms, and Kieselguhr is an amorphous form of silica.

Hence, the correct answer is Option (2).

Example 3
Question:
Silica can react with:
1) HF but not with NaOH
2) NaOH but not with HF
3) both NaOH as well as HF
4) neither NaOH nor HF

Solution:
Silica has a very high Si-O bond enthalpy and is almost non-reactive. However, it is attacked by HF and NaOH. The reactions are given below:

$\mathrm{SiO}_2+2 \mathrm{NaOH} \rightarrow \mathrm{Na}_2 \mathrm{SiO}_3+\mathrm{H}_2 \mathrm{O}$

$\mathrm{SiO}_2+4 \mathrm{HF} \rightarrow \mathrm{SiF}_4+2 \mathrm{H}_2 \mathrm{O}$

Hence, the correct answer is Option (3).

Summary

This compound is versatile, and basic, and is even abundantly available in nature and, therefore, much used in a number of industries. Naturally, this stretches from the sand lying on beaches to screens used on smartphones, huge, thereby underlining the necessity of the compound for both the banal and High-Tech. Different forms of silica and their applications will now be described one by one in this paper. The resiliency and variability of silicon dioxide have made it an essential base both for modern materials science and industry.