Question

Write a notes on 

1. Sheet silicates 

2. Three dimensional silicate

Answer 1

1. Sheet silicates: 

Silicates which contain (Si₂O₅)n^2n- are called sheet or phyllo silicates. In these, Each [SiO₄]^4- tetrahedron unit shares three oxygen atoms with others and thus by forming twodimensional sheets. These sheets, silicates form layered structures in which silicate sheets are stacked over each other. The attractive forces between these layers are very week, hence they can be cleaved easily just like graphite.

Example: Talc, Mica etc… 

2. Three dimensional silicate: Silicates in which all the oxygen atoms of [SiO₄]^4- tetrahedra are shared with other tetrahedra to form three-dimensional network are called three dimensional or tecto silicates. They have general formula (SiO₂)_n .

Examples: 

Quartz. These tecto silicates can be converted into Three dimentional aluminosilicates by replacing [SiO₄]^4- units by [AlO₄]^5- units.

E.g. Feldspar, Zeolites etc.,