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So apparently the Lewis structure of $\ce{SO_2}$ is

enter image description here

It was my understanding that the central atom is the one that is more electronegative. And an atom is more electronegative the closer it is to Fluorine (top-right). Oxygen is definitely closer to fluorine than sulfur is. Then, why is sulfur the central atom?

Also, one thing that has been bugging me for a while: if there are two or more atoms for the central element, how do you make the Lewis structure?

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  • $\begingroup$ can you give example for "two or more atoms for the central element"? $\endgroup$ – Freddy Jul 16 '15 at 7:43
  • $\begingroup$ @Freddy I don't have an example, but I imagine there could be a molecule with two types of elements, and the least electronegative one happens to have two or more atoms. Or is such a thing impossible? $\endgroup$ – Voldemort Jul 16 '15 at 7:54
  • $\begingroup$ I don't know any such molecule. But you can check out chemwiki.ucdavis.edu/Organic_Chemistry/Fundamentals/… $\endgroup$ – Freddy Jul 16 '15 at 8:06
  • $\begingroup$ @Freddy how about H2O2 (just found it in the book)? Oxygen is the central since Hydrogen can't ever be. But I got two oxygens. Apparently the structure looks like this: i.stack.imgur.com/Y39wf.png, but I don't get it: shouldn't the two hydrogens be connected to the same oxygen (because it is the central)? $\endgroup$ – Voldemort Jul 16 '15 at 8:09
  • $\begingroup$ Let's say left oxygen is A and right oxygen is B. Initially both oxygen(without hydrogen) would have 3 lone pair of electron. Then 1st hydrogen will attach lets say oxygen A. Now oxygen A will have 2 lone pair of electrons and oxygen B have 3 lone pair of electron. So naturally 2nd hydrogen will attract towards oxygen B and not to oxygen A. $\endgroup$ – Freddy Jul 16 '15 at 9:49
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I think you messed up something. Because it is exactly opposite.

"Central part of atom is normally least(not the most) electronegative atom i.e. S in this case.

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  • $\begingroup$ What about H2O ? $\endgroup$ – Shahbaaz1104 Jul 11 '17 at 16:29
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For polyatomic molecule least electronegative polyvalent atom acts as central atom and by using this we wlll get most plausible structure (structure having least magnitude of formal charge) for polyatomic molecule.

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