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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: MustangFTW on April 07, 2012, 02:28:00 PM

Title: Lewis Dot structure for HBrO4
Post by: MustangFTW on April 07, 2012, 02:28:00 PM: Hey

Why is the Br the central atom in this structure if O is further to the left (needs more electrons)? is this a special case?
Title: Re: Lewis Dot structure for HBrO4
Post by: juanrga on April 08, 2012, 09:09:31 AM: Quote from: MustangFTW on April 07, 2012, 02:28:00 PM
Hey

Why is the Br the central atom in this structure if O is further to the left (needs more electrons)? is this a special case?

Why do you believe that position in a molecular structure is related to that?
Title: Re: Lewis Dot structure for HBrO4
Post by: JustinCh3m on April 08, 2012, 11:42:42 AM: I think he's referring to the commonly accepted rule that if Carbon is not present, the central atom is usually the lesser electronegative of the choices.

In this case, think of Br as having 4 oxygens attached to it. Where would the H go? On Br?? On one of the O's? You need to apply your systematic rules (see text) for drawing Lewis structures.

I'll give you the first step: how many total valence electrons are present?
Title: Re: Lewis Dot structure for HBrO4
Post by: juanrga on April 09, 2012, 05:19:34 AM: Quote from: JustinCh3m on April 08, 2012, 11:42:42 AM
I think he's referring to the commonly accepted rule that if Carbon is not present, the central atom is usually the lesser electronegative of the choices.

Ok, although I think that the rule that the central atom is usually the unique atom must be more useful. E.g. the central atom in SF₅ is the S; the central atom in ClO₂ is the Cl; the central atom in Cl₂O is the O, even when it is the most electronegative.

In this case the unique atoms are H and Br, and as you pointed the H cannot be the central atom.
Title: Re: Lewis Dot structure for HBrO4
Post by: grs35 on April 09, 2012, 07:18:07 PM: also you should know that O cant have more than 4 bonds. and usually O has 2 bonds and 2 lone pair electrons.