Draw the Lewis structure of ozone (O3) and then determine its molecular geometry.
The Correct Answer and Explanation is:
Based on the chemistry question shown in the image, here is the correct Lewis structure for ozone (O₃) and an explanation of its molecular geometry.
Correct Answer: The molecular geometry of ozone (O₃) is bent.
Lewis Structure of Ozone (O₃)
The correct Lewis structure for ozone features a central oxygen atom double-bonded to one terminal oxygen atom and single-bonded to the other terminal oxygen atom. The central oxygen atom also has one lone pair of electrons.
- The central oxygen atom has a formal charge of +1.
- The double-bonded oxygen atom has two lone pairs and a formal charge of 0.
- The single-bonded oxygen atom has three lone pairs and a formal charge of -1.
It is important to note that ozone exhibits resonance. This means another valid Lewis structure exists where the double and single bonds are swapped. The actual structure is a resonance hybrid of these two forms, with both oxygen-oxygen bonds being identical in length and strength, intermediate between a single and a double bond.
Here is a representation of one of the resonance structures:Generated code
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:O=O — O:
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(In this diagram, the central oxygen has one lone pair, the left oxygen has two lone pairs, and the right oxygen has three lone pairs)
Explanation
To determine the Lewis structure and molecular geometry of ozone (O₃), we first follow the rules for drawing Lewis structures and then apply the Valence Shell Electron Pair Repulsion (VSEPR) theory.
First, we calculate the total number of valence electrons. Oxygen is in Group 16 of the periodic table, so each atom has 6 valence electrons. For O₃, the total is 3 atoms × 6 electrons/atom = 18 valence electrons.
We then arrange the atoms with one oxygen in the center (O–O–O). After forming two single bonds, we use 4 electrons, leaving 14. Distributing these as lone pairs to the outer oxygen atoms first (6 each) uses another 12 electrons, leaving 2 for the central atom. At this point, the central oxygen only has 6 electrons (two bonds and one lone pair), failing the octet rule. To fix this, we move a lone pair from one of the outer oxygens to form a double bond with the central oxygen. This results in the structure described above, which satisfies the octet rule for all atoms and leads to resonance.
To find the molecular geometry, we look at the central oxygen atom. It has three electron groups around it: one single bond, one double bond, and one lone pair. According to VSEPR theory, these three electron groups arrange themselves to be as far apart as possible, resulting in a trigonal planar electron geometry.
However, the molecular geometry describes the arrangement of only the atoms. Since one of the three electron groups is a non-bonding lone pair, it is not included in the final shape of the molecule. With two bonding pairs and one lone pair (an AX₂E₁ system), the resulting shape is bent. The lone pair exerts a stronger repulsive force than the bonding pairs, compressing the O–O–O bond angle to be slightly less than the ideal 120° of a perfect trigonal planar arrangement.
