Diamond is a crystalline allotrope of carbon in which each carbon atom is covalently bonded to four other carbon atoms in a tetrahedral structure.
This strong covalent bonding network results in extremely high bond energy and is responsible for its remarkable properties such as extreme hardness and high thermal conductivity.
Compared to silicon, germanium, and silicon carbide, diamond exhibits the highest bond energy due to the strength and compactness of its C–C bonds.