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Looking here at this website - Omnicalculator, at the section of the website for calculating percentage of ionic character. Omnicalculator - Percentage Ionic Character

They let you choose elements and it calculates percentage of ionic character.

And besides showing the electronegativity difference, and the percentage of ionic character

They show criteria for determining whether something is considered non polar covalent, or polar covalent or ionic

enter image description here

(No doubt the first row of that table they mean non polar covalent)

And they show this graph

enter image description here

I think that table leaves some gaps e.g. what if the electronegativity is < 2, but the percentage ionic character is > 63.21% (Then it's not in any of the three rows).

And they show this graph

Looking at that graph, the second intersection is just above 60. probably 63.21% (the figure they have in their table)

There are some regions of the graph i'm not sure about..'cos their table doesn't cover it.

Any idea how they'd be categorising/classifying sections i've labelled D/E/F?

enter image description here

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1 Answer 1

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The relation of the calculated ionic character and the Pauling electronegativity difference is the function of the ionic character model. There are no regions A-F in this context. There is just the blue curve.

For the measured ionic character, e.g. from the bond length and the bond dipole moment, the graph plays no role and there are just 3 regions nonpolar/polar/ionic according to experimental ionic character value.

Note that the threshold values are not sharply defined, they are rather fuzzy. But there is no reason not to follow the arbitrary values for the calculated values.

Note that the experimental values of ionic character and the difference of Pauling electronegativities are correlated, but not very strongly.

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  • $\begingroup$ Thanks. And so besides 0.5<Δχ<2.0⟹6.06%<IC<63.21%, Also, 6.06%<IC<63.21% ⟹ 0.5<Δχ<2.0 (so that implication goes both ways). And so there are no holes in the table? $\endgroup$
    – barlop
    Commented Dec 30, 2023 at 21:29
  • $\begingroup$ Do you see there any holes? $\endgroup$
    – Poutnik
    Commented Dec 30, 2023 at 21:35
  • $\begingroup$ Not yet but I will check more combinations of elements. $\endgroup$
    – barlop
    Commented Dec 31, 2023 at 1:06
  • $\begingroup$ They aren't truly dependent, rather correlated (not all that well). $\endgroup$
    – Mithoron
    Commented Dec 31, 2023 at 1:07
  • $\begingroup$ I see what you mean re the mapping., I see there's a direct mapping between electronegativity difference and IC. . So the folk that put the IC boundary for ionic at ~63%, use electronegativity difference of 2.. And the folk that put IC boundary for ionic at > 50%, use electronegativity difference at 1.7 or 1.8. calculatoratoz.com/en/percent-ionic-character-calculator/… $\endgroup$
    – barlop
    Commented Dec 31, 2023 at 1:13

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