Account for the followiong

1a)CO₂..covalent due to small cationic size as compared to SiO₂
2.its the ratio of radius of cation to that of anion.....it gives the cordination no., shape of amolecule

CCl4 the carbon atom does not have any vacant d-orbitals so it cannot accept lone pair of electrons from oxygen of water , therefore it does not undergo hydrolysis , while silicon has vacant d-orbitals , so it easily gets hydrolysed....

For 1 b reason given by utd4sver is correct..
1 a Carbon can form π bonds with oxygen but Si cannot form π bonds with oxygen because the overlap b/w the 3p- 2p orbitals is not that effective as compared to the overlap b/w 2p-2p orbitals. So silicon forms a giant structure with oxygen in which each silicon is binded to 4 oxygen atoms which are further binded to other silicon atoms