[Solution from source] All silicates are built from the SiO₄⁴⁻ tetrahedron, with Si at the centre and four O atoms at the corners. Sharing corners gives chains, sheets and frameworks, but the basic unit stays SiO₄⁴⁻. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.