Silicates - Practice Questions & MCQ

A large number of silicates minerals exist in nature. Some of the examples are feldspar, zeolites, mica and asbestos. The basic structural unit of silicates is SiO₄^4– in which silicon atom is bonded to four oxygen atoms in tetrahedron fashion. In silicates either the discrete unit is present or a number of such units are joined together via corners by sharing 1,2,3 or 4 oxygen atoms per silicate units. When silicate units are linked together, they form chain, ring, sheet or three-dimensional structures. Negative charge on silicate structure is neutralised by positively charged metal ions. If all the four corners are shared with other tetrahedral units, three-dimensional network is formed. Two important man-made silicates are glass and cement.

Chain silicates
Chain silicates are formed by sharing two oxygen atoms by each tetrahedral. Anions of chain silicate have two general formula, i.e, (SiO₃)_n^2n- and (Si₄O₁₁)_n^6n-.

Two-dimensional silicates
In such silicates 3-oxygen atoms of each tetrahedral are shared with adjacent SiO₄^4- tetrahedral. Such sharing forms 2-D sheet structure as shown below.