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Why nitrogen is considered to be less electronegative than chlorine. Nitrogen should be more electronegative as I was reading some content about this and I read some reasonable arguments:

  1. $\ce{NCl3}$ in $\ce{H2O}$ gives $\ce{NH3}$ and $\ce{HOCl}$, which proves that nitrogen is negatively charged because it attracts the positively charged hydrogen in $\ce{H2O}$ to form $\ce{NH3}$ and chlorine combines with the negatively charged $\ce{HO-}$ radicals.
  2. $\ce{HNO3}$ is stronger than $\ce{HClO3}$, though chlorine and nitrogen have the same oxidation state ($+5$): $\mathrm{p}K_\mathrm{a}(\ce{HNO3}) = -1.4, \mathrm{p}K_\mathrm{a}(\ce{HClO3}) = -1$.

But in spite of that electronegativity value for nitrogen is considered to be $3.04$ while that of chlorine is $3.16$. Why?

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  • $\begingroup$ Question. It appears as if you've retrieved your values from Wikipedia, however, the measure of dissociation for chloric acid in the article is approximate. The one for nitric acid isn't. I would recommend finding a solid value for chloric acid, first. A cursory search shows little documentation for it. $\endgroup$ – orlando marinella Jun 21 '16 at 16:05
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    $\begingroup$ Depends on the scale used. Allen's definition of electronegativity has nitrogen (3.06) more electronegative than chlorine (2.87). It's a borderline case to compare. $\endgroup$ – Nicolau Saker Neto Jun 21 '16 at 22:44
  • $\begingroup$ Not only is the strength of chloric acid not precisely known, but comparison with nitric acid is not straightforward because the central atoms have different valence electron counts. So where nitric acid has a pi bond, chloric acid has a nonbobding pair on chlorine. $\endgroup$ – Oscar Lanzi Jun 22 '16 at 2:13
  • $\begingroup$ So @OscarLanzi should I compare HNO3 with HClO4 as central atom has utilized all the electrons in each case? $\endgroup$ – User5 Jun 22 '16 at 18:26
  • $\begingroup$ No such comparison really works. You can't cleanly attribute differences in reactivity to differences in electronegativity alone when the elements are in different groups. $\endgroup$ – Oscar Lanzi Jun 22 '16 at 19:01

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