Fluorine, though higher than chlorine in the periodic table, has a very small atomic size. This makes the fluoride anion so formed unstable (highly reactive) due to a very high charge/mass ratio. Also, fluorine has no d-orbitals, which limits its atomic size. As a result, fluorine has an electron affinity less than that of chlorine. See this, archived here.
What should be the oxidation state of $\ce{F}$ in $\ce{HOF}$. As fluorine is the most electronegative element in the periodic table, it should be $-1$. But when I googled it, I found that many so...
Fluorine is the most electronegative element because the definition of electronegativity makes it so. The electronengativity scales are defined based on experimentally determined properties of the elements.
What is the nature of the reaction of attack of fluorine gas on aluminium metal? Is it spontaneous in nature? I have studied reactions of halogens on aluminium, but it had no information about fluo...
Are there stronger oxidizing agents than fluorine gas, so it could oxidize fluoride to fluorine? Also, in case of oxygen, fluorine gas can oxidize oxygen gas to the exotic dioxygenyl ion.
Fluorine is listed as 5 "active" valence electrons, implying perhaps that the 2s electrons do not participate in bonding. Why is fluorine treated differently than oxygen (or does oxygen make compounds where the 2s electrons are more involved in bonding than those of fluorine)?
Lastly, fluorine is much smaller molecule than chlorine, and the shorter distance, or radius, between the nucleus and the electron again makes it more likely to attract the electron and react to gain a noble gas configuration.
6 Fluorine in hydrogen fluoride can form only a limited amount of hydrogen bonds because there is only one (protic) hydrogen atom per fluorine. Ammonium fluoride has enough protic hydrogens to form hydrogen bonds with all four electron pairs on each fluorine — and so they do, in a wurtzite-type arrangement of the ions.