Problem 25 - A Complete Resource Book in Chemistry for JEE Main

Question

\(\left[\mathrm{SiO}_{4}\right]^{4-}\) has a tetrahedral structure and the silicate formed by using three oxygen has a (a) two dimensional sheet structure (b) pyrosilicate structure (c) linear polymeric structure (d) three dimensional structure

Step-by-Step Solution

Answer

The silicate with three oxygen is (a) two dimensional sheet structure.

Step 1: Understanding Silicate Structures

Silicates are structures formed from silicate ext{ ( ext{SiO}_4^{4-})} building blocks. These basic units can polymerize in various ways, such as in sheets, chains, or frameworks, depending on how the oxygen atoms are shared among silicate tetrahedra.

Step 2: Identifying the Structure with Three Oxygen Atoms

When a silicate uses three of its oxygen atoms to connect to other silicates, each of these oxygens is shared with adjacent tetrahedra. Given that three oxygens are shared, it forms a two-dimensional planar structure.

Step 3: Two-Dimensional Sheet Formation

In the two-dimensional sheet silicate structure, each silicon atom shares three out of four oxygen atoms with adjacent tetrahedra, leaving only one oxygen atom available for bonding with other elements.

Step 4: Conclusion

The described scenario matches a two-dimensional sheet structure, where the connection of silicate units via three shared oxygens forms a vast plane or layer. This is commonly seen in minerals like mica and clays.

Key Concepts

Tetrahedral Structure

A tetrahedral structure is fundamental to many silicate minerals. At the heart of this structure is the (\[\mathrm{SiO_4}^{4-}\]), a silicon atom surrounded by four oxygen atoms positioned at the corners of a tetrahedron. This shape is an equilateral triangle when viewed in two dimensions, and perfectly symmetric in three dimensions.

• Silicate tetrahedra are the building blocks of all silicate minerals.
• Each oxygen atom at the vertex of the tetrahedron is available to bond with other elements or other silicate structures.

The way these tetrahedra bond and share oxygen hinges on silicate diversity, forming the basis for different structures such as chains, sheets, and frameworks. Understanding how these tetrahedra can connect is crucial to grasping more complex silicate configurations.

Two-Dimensional Sheet Structure

The two-dimensional sheet structure is a fascinating silicate formation. It occurs when silicate tetrahedra (\[\mathrm{SiO_4}^{4-}\]) share three out of their four oxygen atoms with neighboring tetrahedra. This sharing results in an expansive plane or layer, extending to form sheets at a molecular level.

• Each silicon atom in this type of structure is linked through its oxygen atoms, creating a flat, two-dimensional sheet.
• These sheets stack one over another, but aren't strongly bonded vertically, which explains the layers we see in minerals like mica and clays.

The sheets formed through this structure have significant applications in industry and nature. The weak forces between these layers allow them to slide over one another easily, which is why minerals like mica can be peeled apart in thin sheets.

Silicate Polymerization

Silicate polymerization is the process through which individual silicate tetrahedra (\[\mathrm{SiO_4}^{4-}\]) bond together, sharing oxygen atoms to create larger and more complex structures. The manner in which these tetrahedra connect determines the overall molecular structure of the mineral.

• Polymerization can lead to linear chains, circular rings, expansive sheets, or even three-dimensional frameworks.
• The complexity and variation in silicate structures are due to the different ways oxygen atoms can be shared between two tetrahedra.

This sharing can create single or double chains, or link into sheets or frameworks, which affects the properties and uses of the mineral. With polymerization, silicates can achieve significant strength and complex geometries, leading to their wide range of uses in different applications throughout the geological realm.