Question

The number of shared corners of the constituent SiO4 units in orthosilicate, pyrosilicate, cyclic silicate and sheet silicate, respectively, are

• A. 0, 1, 2 and 3
• B. 2, 3, 0 and 1
• C. 0, 3, 1 and 2
• D. 1, 2, 3 and 0

Hint:

Isolated (ortho) = 0; paired (pyro) = 1; rings (cyclo) = 2; sheets = 3; frameworks (tecto) = 4.

Answer 1

The Correct Option is A

Step 1: In silicates, connectivity is described by how many corners (oxygen atoms) each \(\mathrm{SiO_4}\) tetrahedron shares.
Step 2: Orthosilicates (nesosilicates) have isolated tetrahedra \(\Rightarrow\) share \(0\) corners.
Step 3: Pyrosilicates (\(\mathrm{Si_2O_7^{6-}}\)) have two tetrahedra sharing one oxygen \(\Rightarrow\) share \(1\) corner.
Step 4: Cyclic silicates (\(\mathrm{(SiO_3)_n^{2n-}}\)) form rings where each tetrahedron shares two corners \(\Rightarrow\) \(2\).
Step 5: Sheet (phyllo) silicates (\(\mathrm{(Si_2O_5)_{n}^{2n-}}\)) have extended sheets with each tetrahedron sharing three corners \(\Rightarrow\) \(3\).
Thus the sequence is \(0,1,2,3\).