Which of the following best describes the Lewis structure of $C_3{H}_6{O}_2$ (propanoic acid, $C_2{H}_5{C}_{}{O}_H$)?

• A. A three-carbon chain with all carbons bonded only to hydrogens and no oxygen atoms present.
• B. A three-carbon chain with a terminal carboxylic acid group: the first carbon is bonded to three hydrogens, the second carbon is bonded to two hydrogens, and the third carbon is double-bonded to one oxygen and single-bonded to another oxygen which is bonded to a hydrogen.
• C. A three-carbon chain with a terminal ketone group: the first and third carbons are each bonded to three hydrogens, and the second carbon is double-bonded to an oxygen.
• D. A three-carbon chain with a terminal aldehyde group: the first carbon is bonded to three hydrogens, the second carbon is bonded to two hydrogens, and the third carbon is double-bonded to an oxygen and single-bonded to a hydrogen.

Answer: (B)

Verified step by step guidance

1. Identify the molecular formula given: C\_3H\_6O\_2, which corresponds to propanoic acid, a carboxylic acid with three carbons.
2. Recall the general structure of a carboxylic acid: it contains a carboxyl group (-COOH) at the end of a carbon chain.
3. Draw a three-carbon chain where the first carbon (C1) is bonded to three hydrogens (CH\_3), the second carbon (C2) is bonded to two hydrogens (CH\_2), and the third carbon (C3) forms the carboxyl group.
4. For the carboxyl group on C3, represent it as a carbon double-bonded to one oxygen atom (C=O) and single-bonded to a hydroxyl group (O-H).
5. Verify that all atoms satisfy their typical valencies: carbons have four bonds, oxygens have two bonds, and hydrogens have one bond, ensuring the structure matches propanoic acid.