Silicates Types - classification & structure inorganic chemistry class 11 IIT JEE NEET

Silicate worksheets mcq at: http://www.adichemistry.com/inorganic/p-block/group-14/silicates/silicates-1.html
***
Look around you for a second —
almost everything solid you see on Earth,
like sand, rocks, glass, cement,
is built from silicates.

***
Now here’s the catch —
one single orthosilicate tetrahedral unit
explains the formation of all of them.

In the next few minutes,
I’ll show you how the orthosilicate tetrahedron
connects in different ways
and creates different types of silicates.

***
This is one of the most scoring topics
in Class 11 for IIT-JEE and NEET.

So stay with me till the end.

***
I am Aditya Vardhan,
creator of adichemistry.com, Warangal.

Let us begin
and explore the topic of silicates.

==================
First of all, what are silicates?

Silicates are minerals containing silicon and oxygen,
present in the form of tetrahedral SiO₄ units.

These SiO₄ tetrahedra can link together in several different ways,
giving rise to different types of silicate structures.

==============

Now let us have a closer look at the orthosilicate ion.

The central silicon atom is connected to four oxygen atoms,
arranged tetrahedrally around it.

Each oxygen atom carries a negative charge,
and therefore, the formula of the orthosilicate ion is SiO₄ with 4- charge.

Here, the structure shown is
***the side view of the orthosilicate tetrahedron.

For convenience, we represent the atoms using circles.
***

The blue circles represent the oxygen atoms,
while the red filled circle represents the silicon atom.

***
Most silicate structures are represented on paper in the top view.

So the diagram shown here is the top view *** of the orthosilicate ion.

===========

Now let us build different types of silicates
starting from the orthosilicate ion,
and explore their structures.
==================

The simplest silicates are orthosilicates,
also known as nesosilicates.

They contain only discrete units
of the orthosilicate ion, SiO₄⁴⁻.

In these silicates, the SiO₄ tetrahedra do not share oxygen atoms
with each other.

=============

Some common examples of orthosilicates are:

Phenacite,
Willemite,
Olivine,
and Zircon.

=============
Next are pyrosilicates,
also known as sorosilicates.

They are made up of Si₂O₇⁶⁻ ions,
which are formed by joining two tetrahedral ortho silicate ions.

These two tetrahedra share one oxygen atom at one corner.

The best example of a pyrosilicate is Thortveitite.

===========

The third type of silicates are cyclosilicates,
otherwise known as ring silicates.

They contain (SiO₃)ₙ²ⁿ⁻ ions.

In these silicates, three or more tetrahedral SiO₄⁴⁻ units
are linked together cyclically,
forming ring structures.

Some common examples of cyclosilicates are
Benitoite and Beryl.

===========

Next are chain silicates,
also known as pyroxenes.

They also contain (SiO₃)ₙ²ⁿ⁻ ions.

In these silicates, ‘n’ number of tetrahedral SiO₄ units
are linked linearly,
forming long chain structures.

Some important examples of chain silicates are
Spodumene,
Diopsite,
and Wollastonite.

===============

Now let us look at double chain silicates,
otherwise known as amphiboles.

*** They have the general formula
(Si₄O₁₁)ₙ⁶ⁿ⁻.

In double chain silicates, there are two types of tetrahedra.

***Some tetrahedra share three vertices,
*** while others share only two vertices.

This type of linkage results in a double chain structure.

***Some common examples of amphiboles are
Asbestos
and Tremolite.

============

Next are sheet silicates,
also known as phyllosilicates.

The general formula of sheet silicates is
(Si₂O₅)ₙ²ⁿ⁻.

In these silicates, the SiO₄ tetrahedra share three oxygen atoms
with neighboring tetrahedra.

As a result, the tetrahedra are linked together
to form two-dimensional sheet-like structures.
=================

Common examples of sheet silicates include
talc, mica and clay minerals.

=========
Finally, we have three-dimensional silicates,
also known as tectosilicates.

*** The general formula of three-dimensional silicates is
(SiO₂)ₙ.

*** In these silicates, each SiO₄ tetrahedron shares all four oxygen atoms
with neighboring tetrahedra.

As a result, a continuous three-dimensional network structure is formed.

***
Some important examples of tectosilicates are
quartz, Tridymite, Crystobalite feldspar, and zeolites.

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