a-tin, an allotrope of tin that exists below 132 â, is a semiconductor, while β-tin exists at higher temperatures and is a conductor. As the temperature increases from temperature below 13.2 °C to higher than 13.2 °C energy difference between antibonding orbitals and bonding orbitals increases. energy difference between antibonding orbitals and bonding orbitals decreases. energy difference between the valence band and conduction band increases. energy difference between the valence band and conduction band decreases.