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


1 Answer 1


'e' is a natural 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, you'll need to scroll down the page a bit to the section labelled 'Bond character based on electronegativity differences'.

  • $\begingroup$ Thank you, that is what I thought. just needed some confirmation. That lecture is exactly what I used $\endgroup$
    – Danie
    Commented Jun 21, 2015 at 12:31

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