# Band gap difference in different allotropes of Group4 materials

Diamond and bulk Si are both Group 4 elements found in their $sp^3$ hybridized states, having bandgaps of around 5.3eV and 1.1eV respectively, but Graphene and Silicene are both $sp^2$ hybridized allotropes of the said elements and are zero bandgap materials. What promotes this change in behaviour? Is it the change in hybridization? or the super-aromaticity??

• – CoffeeIsLife Dec 6 '16 at 11:14
• @QuantumAMERICCINO It doesn't say what promotes this behaviour. – ubuntu_noob Dec 7 '16 at 3:55