In the molecule ethene (C_2H_4), what types of orbitals are used to form the sigma bond (bond a) between the two carbon atoms?

• A. p orbitals from each carbon atom
• B. sp^3 hybrid orbitals from each carbon atom
• C. sp^2 hybrid orbitals from each carbon atom
• D. s orbitals from each carbon atom

Answer: (C)

Verified step by step guidance

1. Identify the bonding situation in ethene (C\_2H\_4): the molecule has a double bond between the two carbon atoms, consisting of one sigma (σ) bond and one pi (π) bond.
2. Recall that sigma bonds are formed by the head-on overlap of orbitals, while pi bonds are formed by the side-on overlap of p orbitals.
3. Determine the hybridization of each carbon atom in ethene: since each carbon forms three sigma bonds (two with hydrogen and one with the other carbon) and one pi bond, the carbon atoms are sp\^2 hybridized.
4. Understand that the sigma bond between the two carbon atoms (bond a) is formed by the overlap of sp\^2 hybrid orbitals from each carbon atom, while the pi bond is formed by the overlap of unhybridized p orbitals.
5. Conclude that the correct orbitals forming the sigma bond between the two carbon atoms in ethene are the sp\^2 hybrid orbitals from each carbon atom.