The most used definition of electronegativity is that an element's electronegativity is the power of an atom when in a molecule to attract electron density to itself. The electronegativity depends upon a number of factors and in particuler as the other atoms in the molecule. The first scale of electronegativity was developed by Linus Pauling and on his scale iodine has a value of 2.66 on a scale running from from about 0.7 (an estimate for francium) to 2.20 (for hydrogen) to 3.98 (fluorine). Electronegativity has no units but "Pauling units" are often used when indicating values mapped on to the Pauling scale. On the interactive plot below you may find the "Ball chart" and "Shaded table" styles most useful.
There are a number of ways to produce a set of numbers representing electronegativity and five are given in the table above. The Pauling scale is perhaps the most famous and suffices for many purposes.
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