Question:
Explain the following :
(i) CO2 is a gas whereas SiO2 is solid.
(ii) Silicon forms SiF62- ion whereas the corresponding fluoro compound of carbon is not known.
Solution:
(i) Silicon has a large size compared to carbon. It does not form good π overlapping. It forms four single covalent bonds with oxygen atoms. Each oxygen atom is linked
with two Si atoms. Thus, a large giant molecule of a 3-d structure is formed whereas carbons form a double bond with oxygen atom due to π overlapping.
(ii) Silicon has lower energy 3-d orbital so it can expand its octet givingsp3d2 hybridization while d-orbitals are not present in the valence shell of carbon. It can undergo
sp3-hybridisation only. The size of the carbon atom is very small to accommodate six F- anions.