Lewis structures of ozone

C09-0014. Draw the Lewis structure of ozone, O3, in which the three oxygen atoms are linked in a row. 

Ozone has 142 kJ/mol of excess energy over oxygen, and it is much more reactive. A Lewis structure of ozone shows that the central oxygen atom bears a positive charge, and each of the outer oxygen atoms bears half a negative charge. 

Writing the various Lewis formulas that contribute to a resonance hybrid can be made easier by using curved arrows to keep track of delocalized electrons. We can convert one Lewis structure of ozone to another by moving electron pairs as shown ... 

Compare the Lewis structure of ozone to the Lewis structure of O2 ... 

The Lewis structure of ozone is shown in Figure 11.21a. Note that there are two resonance forms of the molecule. The VSEPR picture showing the geometry of the resonance hybrid. Figure 11.21b, has an 0 — 0 — 0 angle less than 120° due to the presence of the one lone pair. 

In the Lewis structures for the molecules we have discussed to this point, valence electrons have been shown either between two nuclei or associated with a specific atom. These are localized electrons. However, a single Lewis structure does not adequately represent the electronic structures of some molecules. For example, the Lewis structure of ozone (O3) shows one double bond and one single bond. 

Confirm that there is no legitimate Lewis structure of ozone with all zero formal charges. 

When writing a Lewis structure we restrict a molecule s electrons to certain well defined locations either linking two atoms by a covalent bond or as unshared electrons on a sm gle atom Sometimes more than one Lewis structure can be written for a molecule espe cially those that contain multiple bonds An example often cited m introductory chem istry courses is ozone (O3) Ozone occurs naturally m large quantities m the upper atmosphere where it screens the surface of the earth from much of the sun s ultraviolet rays Were it not for this ozone layer most forms of surface life on earth would be dam aged or even destroyed by the rays of the sun The following Lewis structure for ozone satisfies fhe ocfef rule all fhree oxygens have eighf elecfrons m fheir valence shell... 

Seif-Test 2.1 IB Calculate the formal charges for the three oxygen atoms in one of the Lewis structures of the ozone resonance structure (Example 2.5). 

Write the Lewis structure of each of the following reactive species, all of which are found to contribute to the destruction of the ozone layer, and indicate which are radicals (a) chlorine monoxide, CIO (b) dichloroperoxide, Cl—O—O—Cl ... 

The structure of ozone, (a) The Lewis structure shows resonance that involves the bond (blue lines) and one lone pair (red dots), (b) The a bonding framework. 

Ozone, O3, is an essential molecule in the ozone layer. It filters out some of the UV radiation that would otherwise destroy life on Earth. At ground level, ozone is a component in photochemical smog. Draw the Lewis structure for ozone, and indicate whether or not ozone is polar. Can ozone exist in resonance forms ... 

During the long Antarctic night, appreciable amounts of molecular chlorine, Cl, and hypochlorous acid, HOCl, accumulate within the polar vortex. When the sun returns during the spring (in September in Antarctica), ultraviolet radiation decomposes the accumulated molecular chlorine and hypochlorous acid to produce atomic chlorine. Cl. Atomic chlorine is a free radical. Free radicals are atoms or molecules that contain an unpaired or free electron. The Lewis structures of free radicals contain an odd number of electrons. The unpaired electron in free radicals makes them very reactive. The free radical Cl produced from the decomposition of CI2 and HOCl catalyzes the destruction of ozone as represented by the reaction ... 

These two equivalent Lewis structures are called resonance forms. In describing the structure of ozone, we draw both structures and say that ozone is represented by an average of the two structures ... 

Our drawing of the Lewis structure for ozone (O3) satisfied the octet rule for the central atom because we placed a double bond between it and one of the two end O atoms. In fact, we can put the double bond at either end of the molecule, as shown by these two equivalent Lewis structures ... 

Ozone is a very important constituent of the atmosphere. At upper levels, it protects us by absorbing high-energy radiation from the sun. Near the earth s surface, it produces harmful air pollution. Write the Lewis structure for ozone, O3. 

We sometimes encounter molecules and ions in which the experimentally determined arrangement of atoms is not adequately described by a single dominant Lewis structure. Consider ozone, O3, which is a bent molecule with two equal O—O bond lengths ( FIGURE 8.12). Because each oxygen atom contributes 6 valence electrons, the ozone molecule has 18 valence electrons. This means the Lewis structure must have one O — O single bond and one 0 = 0 double bond to attain an octet about each atom ... 

There is no reason for one of these Lewis structures to be dominant because they are equally valid representations of the molecule. The placement of the atoms in these two alternative but completely equivalent Lewis structures is the same, but the placement of the electrons is different. Lewis structures of this sort are called resonance structures. To describe the structure of ozone properly, we write both resonance structures and use a double-headed arrow to indicate that the real molecule is described by an average of the two ... 

Chlorofluorocarbons have been used as refrigerants for the past 50 years, but their use is now being phased out worldwide because of concerns about atmospheric ozone depletion. Draw the Lewis structure of dichlorodifluoromethane, CF2CI2, also known as DuPont s Freon-12. 

It is not possible to write a Lewis structure for ozone without separation of charges. 

The two Lewis structures I and II are known as the resonance structures for the ozone molecule. The two alternative Lewis structures for ozone are equivalent except for the position of valence electrons. The term resonance refers to a molecule or polyatomic ion in which two or more possible Lewis structures can be drawn, but not the actual structure. 

This Lewis formula, however, is inconsistent with the experimentally determined stmc-ture. On the basis of the Lewis formula, we would expect ozone to have two different O—O bond lengths, one of them similar to the O—O single bond distance of 147 pm in hydrogen peroxide (HO—OH) and the other similar to the 121 pm double bond distance in O2. In fact, both bond distances are the same (128 pm)—somewhat shorter than a single bond, somewhat longer than a double bond. The structure of ozone requires that the central oxygen must be identically bonded to both terminal oxygens. 

An atom s formal charge is calculated as follows We can illustrate the concept of formal charge using the ozone molecule (O3). Use the step-by-step method for drawing Lewis structures to draw the Lewis structure for ozone, and then determine the formal charge on each O atom by subtracting the number of associated electrons from the number of valence electrons. 

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