Which of the following molecules contains only single bonds?

• A. $C_2{H}_2$ (acetylene)
• B. $C_2{H}_4$ (ethylene)
• C. ${\mathrm{CO}}_2$ (carbon dioxide)
• D. ${\mathrm{CH}}_4$ (methane)

Answer: (D)

Verified step by step guidance

1. Identify the molecular formulas and their common names: C\_2H\_2 (acetylene), C\_2H\_4 (ethylene), CO\_2 (carbon dioxide), and CH\_4 (methane).
2. Recall the types of bonds present in each molecule by considering their bonding and structure: acetylene has a triple bond between carbons, ethylene has a double bond between carbons, carbon dioxide has double bonds between carbon and oxygen, and methane has only single bonds between carbon and hydrogen.
3. Understand that single bonds involve the sharing of one pair of electrons between atoms, double bonds share two pairs, and triple bonds share three pairs.
4. Analyze each molecule's bonding: acetylene (C\_2H\_2) contains a carbon-carbon triple bond, ethylene (C\_2H\_4) contains a carbon-carbon double bond, carbon dioxide (CO\_2) contains two carbon-oxygen double bonds, and methane (CH\_4) contains only carbon-hydrogen single bonds.
5. Conclude that methane (CH\_4) is the molecule that contains only single bonds.