Coordination in SiO2 Network Structure

Steps:

• Silicon in SiO2 forms a tetrahedral lattice, bonding to four oxygen atoms via sp3 hybridization.
• Each oxygen atom, with two lone pairs, bridges two silicon atoms to complete its octet.
• The Si-O bonds share electrons equally due to similar electronegativities, classifying them as covalent.
• Empirical formula SiO2 confirms 1:2 Si:O ratio, matching x=4, y=2.

Why C is correct:

• SiO2's giant covalent structure requires each Si to form four covalent bonds (Pauling's rules for silicates) and each O to link two Si atoms.

Why the others are wrong:

• A: x=2 and y=1 imply linear chains, not tetrahedral SiO2 lattice.
• B: x=2 and y=1 mismatch coordination; bonds are covalent, not ionic.
• D: Coordination is correct, but Si-O bonds are covalent, not ionic (electronegativity difference <1.7).

Final answer: C