Question

In graphite how can each carbon be bonded with only three carbons.and called stable??

Answer 1

Graphite is sp2 hybridized, and the sp2 hybrid orbitals participate in covalent bond formation, the unhybridized p-orbital participates in pi-bonding. .
Graphite has delocalized pi-electrons over the entire sheet
This delocalization lowers the energy of the system, leading to greater thermodynamic stability.
Delocalization of electrons or greater conjugation - enhances the thermodynamic stability..
In diamond the interaction is only between neighbouring carbon atoms.
In Graphite the delocalization of pi-electrons is over the entire 2-dim layer >
although u can say graphite have an extra electron but diamond donot have that .
thats the reason behind it .