Re: How did Pauling come up with 4 as the electronegativity for F ? Is it 3.98?

The commonly accepted value of electronegativity for Fluroine (as accepted 
in most textbooks and sources I've run across) is 4.00, which is what 
Pauling DECIDED. The value of 3.98 is probably derived from the 
Allred-Rochow tabulation or the Mulliken Electronegativity scale.Pauling is 
the first chemist, I believe, to actual quantify electronegativey values. 
He ASSIGNED Fluorine a value of 4.0 and was able to scale all the other 
elements by measuring and deriving electronegativity differences. I don't 
believe there was an absolute scale to work with. He had to experimentally 
determine electronegativity differences and arbitrarily assign the biggest 
baddest electron gobbler, fluorine a value. The discrepency between 
Pauling's 4.0 and other scales' use of 3.98 is probably due to the fact 
that Pauling calculated electronegativety values from a rather complicted 
wave funtion analysis which I won't go into here (I'm not even sure I 
completly understand it myself !). The other scales tend to use simple 
functions based of ionization potential and/or electron affinity and there 
is probably some sources of error with the values in IP and EA. In any 
case, an electronegativity value difference of .02 is not enough to cause 
any doubt in what type of bonds would form. Fluorine very much wants to 
form highly ionic bonds and a difference of .02 is not going to change the 
character of the bond. Here are some more detailed links;

http://www.umich.edu/~chem302/lecturesummary/200summaries_BH/electronegativ
ity.html

http://dbhs.wvusd.k12.ca.us/Bonding/Electroneg-development.html