Pauling's equation on the relationship between Electronegativity and Percentage Ionic Character [closed]








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In Paulings eqn:


$$ \%~\ce{ionic~character} = \left[ 1−e^{−(Δχ/2)^2}\right] \times 100$$


What is $e$?


I for the love of me can't find it anywhere




'e' is a [natural exponential function](https://en.wikipedia.org/wiki/Exponential_function), so not an actual measurement.


The equation is correctly written as:


% Ionic character $= (1 − e^{−(\frac{Δχ}{2})^2})×100$


where the $−(\frac{Δχ}{2})^2$ term is raised as a power of the natural exponent 'e'.


Source: The University of the West Indies page [Lecture 3. Polarizability](http://wwwchem.uwimona.edu.jm/courses/CHEM1902/IC10K_MG_Fajans.html), you'll need to scroll down the page a bit to the section labelled 'Bond character based on electronegativity differences'.


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