Lewis Structure of BrO2- vs ClO2-

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K Honeychurch 1K
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Lewis Structure of BrO2- vs ClO2-

Postby K Honeychurch 1K » Tue Dec 09, 2014 11:14 pm

The structure of BrO2- has Br single bonded to each O. The Br has 2 lone pairs and each O has 3 lone pairs.
The structure of ClO2- has Cl double bonded to one O and single bonded to the other O. The Cl has 2 lone pairs, the first O has 2 lone pairs and the other O has 3 lone pairs. There are 2 resonance structures.
(Question 3B/C of the Fall 2009 Exam pg 212 of the course reader shows both structures)
What accounts for the difference in lewis structures of BrO2- and ClO2-? Wouldn't BrO2- be more stable (due to formal charges) if it had the same structure as ClO2-?

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Re: Lewis Structure of BrO2- vs ClO2-

Postby Chem_Mod » Wed Dec 10, 2014 11:30 pm

The electronegativity difference between O and Cl is smaller than that of O and Br therefore O is more likely to "give up" one of its lone pairs to form a shared double bond with Cl. The larger electronegativity difference between O and Br causes the O to keep possession of that lone pair.


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