Which of the following best describes the Lewis dot structure of the neutral compound C2H2 (ethyne)?

• A. The two carbon atoms are connected by a single bond, and each carbon has three hydrogen atoms attached.
• B. The two carbon atoms are connected by a triple bond, and both hydrogens are attached to the same carbon atom.
• C. Each carbon atom is connected by a triple bond, and each carbon has one hydrogen atom attached.
• D. Each carbon atom is connected by a double bond, and each carbon has two hydrogen atoms attached.

Answer: (C)

Verified step by step guidance

1. Step 1: Determine the total number of valence electrons available for bonding in C2H2. Carbon has 4 valence electrons and hydrogen has 1 valence electron. Since there are 2 carbons and 2 hydrogens, calculate the total valence electrons as: \$2 \times 4 + 2 \times 1$.
2. Step 2: Recognize that the molecule is neutral, so the total number of valence electrons calculated will be used to form bonds and satisfy the octet rule for carbon atoms and the duet rule for hydrogen atoms.
3. Step 3: Consider the bonding possibilities between the two carbon atoms. Carbon atoms can form single, double, or triple bonds. The structure must allow each carbon to have a full octet and each hydrogen to have 2 electrons (a duet).
4. Step 4: Evaluate the options given: a single bond between carbons with three hydrogens on each carbon would exceed the number of hydrogens in the formula; a triple bond between carbons with both hydrogens on the same carbon would not satisfy the molecular formula C2H2; a double bond with two hydrogens on each carbon would also exceed the number of hydrogens.
5. Step 5: Conclude that the correct Lewis structure has a triple bond between the two carbon atoms, with each carbon atom bonded to one hydrogen atom, satisfying both the octet rule for carbon and the duet rule for hydrogen, and matching the molecular formula C2H2.