Question

though carbon and silicon have same properties , why bonds of silicon end upto only 7 or 8 and are less stable than that of carbon?

Answer 1

The catenation property of carbon and silicon result into the long chains of same element. Carbon and silicon have various similarities but the main difference if in their electronic configuration. Silicon have vacant d- orbitals whereas carbon does not have vacant d- orbitals due to which carbon is able to form multiple bonds. Silicon can not make multiple bonds. The other difference is in their electonegativity. The carbon has small size and higher electronegativity than silicon.
Carbon-Carbon bond is more stronger than the Si-Si bond. On the other hand, Si-O and Si-H are stronger than that of Si-Si bond.
The C-C, C-O, C-H bonds have nearly same strength. That's why Carbon can form large chain and silicon can not.