A) \[SiO_{4}^{4-}\]
B) \[S{{i}_{2}}O_{7}^{6-}\]
C) \[{{\left( S{{i}_{2}}O_{5}^{2-} \right)}_{n}}\]
D) \[{{\left( SiO_{3}^{2-} \right)}_{n}}\]
Correct Answer: D
Solution :
(i) Orthosilicates: These contain discrete \[{{[Si{{O}_{4}}]}^{4-}}\] units i.e., there is no sharing of comers with one another. (ii) Pyrosilicate: In these silicates two tetrahedral units are joined by sharing oxygen at one comer thereby giving \[{{[S{{i}_{2}}{{O}_{7}}]}^{6-}}\] units. (iii) Cyclic silicates: If two oxygen atoms per tetrahedron are shared to form closed rings such that the structure with general formula \[(SiO_{3}^{2-})\,\,or\,\,{{(Si{{O}_{3}})}_{a}}^{2-}\] is obtained, the silicates containing these anions are called cyclic silicates \[S{{i}_{3}}{{O}_{9}}^{6-}\,and\,S{{i}_{6}}{{O}_{18}}^{12-}\] anions are the typical examples of cyclic silicates. (iv) Chain silicates : Chain silicates may be further classified into simple chain & double chain compounds. In case of simple chains two comers of each tetrahedron are shared & they form a long chain of tetrahedron. Their general formula is also same as the cyclic silicates i.e. \[{{(Si{{O}_{3}})}_{n}}^{2n-}\] (v) Two dimensional sheet silicates: In such silicates, three oxygen atoms of each tetrahedral are shared with adjacent\[SiO_{4}^{4-}\] tetrahedrals. Such sharing forms two dimension sheet structure with general formula \[{{(S{{i}_{2}}{{O}_{5}})}_{n}}^{2n-}\] (vi) Three dimensional sheet silicates: These silicates involve all four oxygen atom in sharing with adjacent \[SiO_{4}^{4-}\] tetrahedral units.
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