In silicon dioxide

Silicon dioxide, $$SiO_2$$, does not exist as discrete $$SiO_2$$ molecules. Instead, it forms a three-dimensional covalent network similar to quartz.

Key structural features of this network:

1. Each silicon atom is at the centre of a regular tetrahedron formed by four oxygen atoms. The $$Si-O$$ bond length is the same for all four bonds.
2. Each oxygen atom acts as a bridge (a “bridging oxygen”) between two different silicon atoms. Hence an oxygen completes its octet by forming two single $$Si-O$$ bonds, one to each adjacent silicon.

Because of this extended network:

• Every silicon atom has a coordination number of 4 (tetrahedral).
• Every oxygen atom has a coordination number of 2.
• All $$Si-O$$ bonds are single bonds; there are no $$Si=O$$ double bonds in the solid.

Now check the options:

Option A: “Each silicon atom is surrounded by four oxygen atoms and each oxygen atom is bonded to two silicon atoms.” — This matches the network described above. ✔️

Option B: Gives coordination 2 for silicon, which is incorrect. ✖️

Option C: Again states silicon is bonded only to two oxygens, wrong for the network solid. ✖️

Option D: Mentions double bonds $$Si=O$$, which are absent in crystalline $$SiO_2$$. ✖️

Therefore, the correct statement is:

Option A which is: Each silicon atom is surrounded by four oxygen atoms and each oxygen atom is bonded to two silicon atoms.