In a Lewis dot structure of ethene (C_2H_4), which arrows would point to electrons involved in a pi bond?

• A. Arrows pointing to the electrons shared between carbon and hydrogen atoms
• B. Arrows pointing to the electrons in lone pairs on the carbon atoms
• C. Arrows pointing to the electrons in the sigma bond between the two carbon atoms
• D. Arrows pointing to the electrons shared between the two carbon atoms above and below the plane of the molecule

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the bonding in ethene (C_2H_4). Ethene consists of two carbon atoms double bonded to each other, and each carbon is also bonded to two hydrogen atoms.
2. Step 2: Recall that a double bond consists of one sigma (σ) bond and one pi (π) bond. The sigma bond is formed by the head-on overlap of orbitals, while the pi bond is formed by the side-to-side overlap of p orbitals.
3. Step 3: Identify the electrons involved in the pi bond. These electrons are located in the p orbitals on each carbon atom that overlap above and below the plane of the molecule, creating the pi bond.
4. Step 4: Recognize that electrons shared between carbon and hydrogen atoms are involved in sigma bonds, not pi bonds, and carbon atoms in ethene do not have lone pairs, so no arrows point to lone pair electrons on carbon.
5. Step 5: Conclude that arrows pointing to the electrons shared between the two carbon atoms above and below the plane of the molecule correctly indicate the electrons involved in the pi bond.