Why is silicon dioxide a solid?

Answer 1

Silicon dioxide is not like carbon dioxide ( forms double bond with oxygen); this is expalined because it's energetically unfavourable for silicon dioxide to form double bond. 2p and 3p overlap b/w silicon and oxygen is not energetically favorable, so instead silicon binds covalent with 4 oxygen atoms( single bond) and forming a crystalline solid shape.

Answer 2

Both SiO2 and CO2 seem to have similar linear structure but no, not really.

In case of SiO2 Silocon didn't form double bond with oxygen, instead, Silicon form single bond with each oxygen and allow oxygen to share the other leg to another Silicon atom. Stucture of SiO2 is a large covalent network structure. It is not appropriate to write SiO2 as [SiO2]n because we don't know where this n end to. So this is why the glass is solid to us.

Answer 3

Carbon can form double bonds to oxygen allowing carbon to achieve an octet, silicon cannot, there is next to no evidence for a Si=O. It is all due to poor overlap between 3p orbital on Si and the 2p orbital on O.

Silicon goes down the polymerisation route, silicon atoms surrounded tetrahedrally by oxygen atoms that bridge between silicon atoms.

Interestingly high pressure results (2007) for carbon dioxide show that at high (> 1GPa, 10,000 atmospheres) it polymerises to form giant molecular

forms which have similarities to silicon dioxide.

Answer 4

Silicon dioxide is hard because it is a covalent compound and it has the structure of diamond and diamond is hard.