Question

Account the following
a)elemental silicon does not form graphite like structure.
b) +2 oxidation state of lead is more stable than +4 orbital state

Answer 1

a) The orbitals overlap to a significant degree, which means that pi-bonds can easily form. The green atoms to the right are silicon. You can see that, because of the larger atomic radius, the p-orbitals don't overlap as much, meaning that double bonds are generally not favorable in silicon.

b)With tin, the +4 state is still more stable than the +2, but by the time you get to lead, the +2 state is the more stable - and dominates the chemistry of lead.