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Background

A fundamental concept imparted at the beginning of organic chemistry is electronegativity. $\ce{N, O, F}$ and $\ce{Cl}$ are particularly electronegative and are capable of shifting the electron cloud of bonded atoms towards themselves in resonance, which I have read recently.

While reading about haloarenes, I encountered this statement "In aryl halides, a $\ce{C-X}$ bond acquires partial double bond character due to resonance, and subsequently the halogen atom acquires partial positive charge"

Question

How is the above statement true? Isn't chlorine more electronegative? How does it acquire positive charge? Isn't inductive effect stronger than resonance effect?

Picture is attached for resonance

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  • $\begingroup$ That's formal charge in those structures. Also there's noting strange in opposite effects. $\endgroup$ – Mithoron Dec 9 '18 at 23:33
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Chlorine atom has complete octet in all of the resonating structures. So in short it has stable electronic configurations in all of them. Generally, anything that has got a lone pair and has complete octet can donate in a similar manner. Oxygen and nitrogen, for instance in phenol and aniline.

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  • $\begingroup$ But what about the -I effect ,and benzene ring is electron rich . Also even in water molecule oxygen atom has an octet but still it has a partial -ve charge $\endgroup$ – sudhanva b Dec 16 '18 at 14:37
  • $\begingroup$ @sudhanvab halogens donate by resonance and withdraw by inductive effects. $\endgroup$ – user204049 Dec 16 '18 at 17:41
  • $\begingroup$ But inductive effect is stronger and resonance effect $\endgroup$ – sudhanva b Dec 17 '18 at 14:14

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