Consider the Lewis structure for ozone (O3) proposed by a student in General Chemistry: Which of the following statements 10-0-01 about this structure is incorrect?
The Correct Answer and Explanation is :
To accurately address this, let’s first break down the Lewis structure of ozone (O₃) and the common misconceptions about it. Ozone (O₃) is a molecule that contains three oxygen atoms. The central atom in the structure is oxygen, and it is bonded to two other oxygen atoms via a combination of single and double bonds, along with formal charges.
Correct Lewis Structure of Ozone (O₃):
- Bonding: The central oxygen atom in O₃ forms a double bond with one oxygen atom and a single bond with the other oxygen atom. However, the electrons are delocalized across the molecule due to resonance, meaning that the bonds are neither purely single nor purely double. Instead, the actual bonding is an average of these two forms.
- Formal Charges: In the most common Lewis structure of ozone, the central oxygen atom has no formal charge, one of the outer oxygen atoms has a formal charge of -1, and the other outer oxygen atom has a formal charge of +1. The negative charge is placed on the oxygen atom with the single bond, and the positive charge is placed on the oxygen atom with the double bond. This helps to minimize the formal charges across the molecule.
- Resonance: Ozone undergoes resonance, meaning the electrons move between the bonds to create two possible forms that are equivalent. This results in the actual structure being a hybrid of these two forms.
Common Incorrect Statements:
- Incorrect Statement: “Ozone has a linear structure with 180° bond angles.”
- Why It’s Incorrect: The geometry of ozone is bent or V-shaped, not linear. The bond angles in O₃ are approximately 117°, which is characteristic of a bent shape due to the lone pairs on the central oxygen atom. The molecule does not follow the linear shape expected in molecules with no lone pairs on the central atom (e.g., CO₂).
Conclusion:
The incorrect statement is that ozone has a linear structure with 180° bond angles. This is inaccurate because ozone has a bent structure, with bond angles of approximately 117° due to the lone pairs on the central oxygen atom. The delocalized nature of the bonding (resonance) and the presence of formal charges help stabilize the molecule, contributing to its unique properties.