Question

Which of the following anions is present in the chain structure of silicates?

• A. (Si\(_2\)O\(_5^{2-}\))\(_n\)
• B. (Si\(_2\)O\(_3^{2-}\))\(_n\)
• C. Si\(_2\)O\(_4^{4-}\)
• D. Si\(_2\)O\(_7^{6-}\)

Hint:

The ratio of Si:O in chain silicates is 1:3, given by the formula (SiO\(_3^{2-}\))\(_n\).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Silicates are classified based on the arrangement of SiO\(_4^{4-}\) tetrahedra. Chain silicates (pyroxenes) have a structure where two oxygen atoms per tetrahedron are shared.

Step 2: Detailed Explanation:
In chain silicates (inosilicates), each SiO\(_4\) tetrahedron shares two of its oxygen atoms with neighboring tetrahedra, forming long chains. The general formula for a single-chain silicate is (SiO\(_3^{2-}\))\(_n\). This can also be written as (Si\(_2\)O\(_5^{2-}\))\(_n\), which simplifies to SiO\(_3^{2-}\) per unit.
• (A) (Si\(_2\)O\(_5^{2-}\))\(_n\): Correct formula for chain silicates (e.g., pyroxenes). • (B) (Si\(_2\)O\(_3^{2-}\))\(_n\): Incorrect. • (C) Si\(_2\)O\(_4^{4-}\): This is a discrete anion (pyrosilicate), found in sorosilicates. • (D) Si\(_2\)O\(_7^{6-}\): This is also a discrete anion, found in sorosilicates.

Step 3: Final Answer:
The anion present in chain silicates is (Si\(_2\)O\(_5^{2-}\))\(_n\), which corresponds to option (A).