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What is the exact electronegativity differece value of determinig whether a compound is ionic or covalent? Is it 1.7 or 2.1?

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closed as off-topic by NotEvans., Jon Custer, Jan, Tyberius, Mithoron Sep 4 '17 at 17:45

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    $\begingroup$ The short answer is neither. A bond's degree of ionic behavior depends on the model used, the compound at hand, and the scale of electronegativity. If you define it through dipole moment (at least 50% of elementary charge on each 'atom'), and use Pauling's classical electronegativity, and restrict yourself to diatomic compounds, I believe a simplified derivation shows it is $1.7$. (continues) $\endgroup$ – Linear Christmas Sep 4 '17 at 15:35
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    $\begingroup$ There is nothing exact about it. Use any value you like. It is arbitrary anyway. $\endgroup$ – Ivan Neretin Sep 4 '17 at 15:35
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    $\begingroup$ (continues) This does not mean it is accurate, or that the compound with $|EN| \ge 1.7$ will show properties you would associate with a typical ionic compound. Part of the reason is that even the dipole moment is not an accurate measure of a bond's ionic degree; it is affected by other electrons at each constituent 'atom'. There are also other models, and like 20 something different scales (many of which are disguised as pseudo-Pauling for convenience), two-dimensional analysis (less error prone, predicts metallic bond), etc etc $\endgroup$ – Linear Christmas Sep 4 '17 at 15:38
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    $\begingroup$ If you wish to skip the literature overview, I suggest reading two papers by Sproul (J Chem Edu, 70, 7, 1993, p 531; J Chem Edu, 78, 3, 2001, p 387) and one by Meek, Garner (J Chem Edu, 82, 2, 2005, p 325). $\endgroup$ – Linear Christmas Sep 4 '17 at 15:53
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    $\begingroup$ I'm voting to close this question as off-topic because it's based on false premise. $\endgroup$ – Mithoron Sep 4 '17 at 17:45

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