Silicates

In chemistry, a silicate is any member of the silicate family of anions, which is composed of the elements silicon and oxygen. The orthosilicate SiO44-, metasilicate SiO32-, and pyrosilicate Si2O76-  are all members of the silicate family. In addition to such anions, the term is used to refer to any salts of such anions such as sodium metasilicate, as well as any ester that contains the corresponding chemical group such as tetramethyl orthosilicate.

Silicate anions are often large polymeric molecules that can take on a wide variety of shapes, such as chains and rings (as in polymeric metasilicate [SiO32-]n), double chains (as in [Si2O52-]n), and sheets (as in [Si2O52-]n). Silicate anions are also known as silicate cations.

A silicate mineral, an ionic solid with silicate anions, and a rock type that is primarily composed of such minerals are all referred to as silicates in geology and astronomy, and they are all classified as such.

The term “silicate” is sometimes used to refer to any anions containing silicon, even if they do not conform to the general formula or contain atoms other than oxygen; for example, hexafluorosilicate [SiF6]2- is sometimes referred to as “silicate.”

Chemical properties:

Generally speaking, solid silicates are stable and well-characterised compounds.

In contrast to sodium ortho- and metasilicate, silicates containing alkali cations and small or chain-like anions, such as sodium ortho- and metasilicate, are relatively water-soluble. When they are crystallised from solution, they form a number of solid hydrates. In fact, soluble sodium silicates and mixtures of sodium silicates, collectively known as waterglass, are important industrial and household chemicals. At normal conditions, silicates of non-alkali cations, as well as those containing sheet and tridimensional polymeric anions, have negligible solubility in water.

Detection: In solution, silicate anions react with molybdate anions, resulting in the formation of yellow silicomolybdate complexes. The reaction of monomeric orthosilicate was found to be complete in 75 seconds, that of dimeric pyrosilicate in 10 minutes, and that of higher oligomers in a significantly longer period of time. It has been observed that the reaction does not occur with colloidal silica suspensions in particular.

Zeolite formation: The nature of soluble silicates is important for understanding biomineralization and the synthesis of aluminosilicates, such as the catalysts known as zeolites, which are used in a variety of industrial applications.

Silicon and oxygen:

It is composed of the SiO4 anionic group, or a silicon atom with four surrounding oxygen atoms arranged to define the corners of the tetrahedron, and four oxygen atoms in the centre of the tetrahedron. This is a critical component of the majority of silicates found in the Earth’s crust. A variety of silicate minerals can be distinguished by the differences in the tetrahedra links between them, as well as by the presence or absence of cations in the mineral.

There are five types of silicon–oxygen tetrahedra links that are commonly found:

• Independent tetrahedra are a type of polyhedra.

• Single-stranded chains. 

• Double chains are a type of chain that is made up of two links that are connected together.

• Sheet silicates are a type of silicate.

• Silicates of the framework.

Independent tetrahedra: The tetrahedra in this group do not share any oxygen atoms and are therefore considered to be independent. The tetrahedra and positive ions are attracted to one another, which holds minerals with this structure together. Cations of metals, such as iron or magnesium, could be present in the positive ions. Olivine is a common mineral found in this group of minerals.

Single chains: Tetrahedra link together to form a chain in single-chain silicates by sharing two oxygen atoms with one another. Pyroxene is a mineral that is found in abundance in this group.

Double chains: Silicates with double-chain structures are formed when tetrahedra join together to form a double chain (not always, but mostly) by sharing two or three oxygen atoms between them. Amphiboles are a type of mineral that is commonly found in this group.

Sheet silicates: Tetrahedra in this group all share three oxygen atoms between them, which allows them to link together to form two-dimensional sheets. This structure does result in minerals in this group having a single strong cleavage plane as a result of the structure. Micas are included in this category. Both muscovite and biotite have extremely thin layers that can be peeled away in sheets, similar to acetate.

Framework Silicates: As each tetrahedron shares all four oxygen atoms with its neighbours, the resulting structure is three-dimensional four-dimensional (three-dimensional four-dimensional). This category includes minerals such as quartz and feldspar.

Sodium metasilicates:

In the chemical world, sodium metasilicate (Na2SiO3) is the chemical compound with the formula Na2SiO3 that serves as the primary component of commercial sodium silicate solutions. It is an ionic compound which contains the sodium cations Na+ and the polymeric metasilicate anions [–SiO23- ]n, which are both Na cations. It is a colourless, crystalline, hygroscopic, and deliquescent solid that is soluble in water (producing an alkaline solution), but not in alcohols or other organic solvents (such as acetone).

Properties :

Sodium oxide Na2O can be used to prepare the anhydrous compound by fusing silicon dioxide SiO2 (silica, quartz) with sodium oxide Na2O (in a 1:1 molar ratio).  

The compound crystallised from solution as a variety of hydrates, including but not limited to, 

Na2SiO3.5H 2O is a pentahydrate of sodium and silicon. 

Na2SiO3.9H2O is a nonahydrate of sodium silicate.

Conclusion:

Silicates are minerals that contain silicon and oxygen in the form of tetrahedral SiO44- units that are linked together in a variety of ways.

Silicate anions are often large polymeric molecules that can take on a wide variety of shapes, such as chains and rings (as in polymeric metasilicate [SiO3 2-]n), double chains (as in [[Si2O5 2-]n)), and sheets (as in [Si2O5 2-]n). Silicate anions are also known as silicate cations.The term “silicate” is sometimes used to refer to any anions containing silicon, even if they do not conform to the general formula or contain atoms other than oxygen. 

It is composed of the SiO4 anionic group, or a silicon atom with four surrounding oxygen atoms arranged to define the corners of the tetrahedron, and four oxygen atoms in the centre of the tetrahedron.

In the chemical world, sodium metasilicate (Na2SiO3) is the chemical compound with the formula Na2SiO3 that serves as the primary component of commercial sodium silicate solutions.It is a colourless, crystalline, hygroscopic, and deliquescent solid that is soluble in water (producing an alkaline solution), but not in alcohols or other organic solvents.