Consider the molecule ethene ($C_2{H}_4$). How many sigma and pi bonds are present in this molecule?

• A. $6$ sigma bonds and $0$ pi bonds
• B. $3$ sigma bonds and $2$ pi bonds
• C. $5$ sigma bonds and $1$ pi bond
• D. $4$ sigma bonds and $2$ pi bonds

Answer: (C)

Verified step by step guidance

1. Start by drawing the Lewis structure of ethene (C\_2H\_4). Ethene consists of two carbon atoms double bonded to each other, with each carbon atom bonded to two hydrogen atoms.
2. Recall that a single bond consists of one sigma (σ) bond, and a double bond consists of one sigma (σ) bond and one pi (π) bond.
3. Count the sigma bonds: Each C–H bond is a single bond, so each is one sigma bond. Since there are four C–H bonds, that gives 4 sigma bonds. The C=C double bond contains one sigma bond, so add 1 more sigma bond.
4. Count the pi bonds: The C=C double bond has one pi bond in addition to the sigma bond, so there is 1 pi bond in ethene.
5. Sum up the total bonds: Total sigma bonds = 4 (C–H) + 1 (C=C) = 5 sigma bonds; Total pi bonds = 1 (from the C=C double bond).