In ethane, carbon atoms are sp3 hybridised and form how many sp3 orbitals per carbon?

• A. 2
• B. 3
• C. 4
• D. 5

Answer: (C)

sp3 hybridisation on carbon gives four equivalent orbitals that point toward the corners of a tetrahedron. Each of these sp3 orbitals can form a sigma bond. In ethane, each carbon forms four sigma bonds: three to hydrogen atoms and one to the other carbon. So, per carbon, there are four sp3 orbitals involved. This reflects carbon’s valence of four and the bonding pattern in ethane. The unhybridized p orbitals aren’t used here because all four valence orbitals are hybridized into sp3.