Question

How do you use electronegativity values to determine the one element that always has a negative oxidation number when it appears in any binary compound?

Answer 1

Well, which is the most electronegative element.........?

Explanation:

On most electronegativity scales, fluorine is the most electronegative element. What does electronegativity mean? It is conceived to be the ability of an atom involved in a chemical bond to polarize electron density towards itself.

So let's look at some simple compounds (or molecules) of fluorine: interhalogens, `F-X`; and `OF_2`. The oxidation states of the heteroatom are `X^(+I)` and `O^(+II)`, and of course we have `F^(-I)`. What is the oxidation number of fluorine in molecular fluorine, `F_2`?

As a curiosity that speaks to fluorine's oxidizing ability, and reactivity, some fluorine chemists I have met are missing eyes or fingers after a laboratory accident. Fluorine chemistry is to be approached with care.